Here is my version of the answer:
Bass from Stack Exchange solved it as follows:
Deductions used:
E is next to both D and L, so it can be placed.
R is next to E, and it needs to be able to reach the B in ROB, so the R is placed.
A is next to M, and it must have at least 4 unknown neighbours to house all of C,X,N and H. So the A is placed.
with CXNH around the A, ACQUIRE won't fit onto the three top rows anymore, so the C is placed.
Now WHAM places the H
AXLE disambiguates the N and X around the A
U must be adjacent to C, J and S, so it's placed.
ACQUIRE now places the Q and I
the T in JUST is now forced
P must be adjacent to both I and R, so it is placed
O in ROB is now forced
which in turn forces the V in derv (which is some sort of diesel vehicle, it seems)
the K in KEG has only one spot left
and even without using the remaining clue (FIR) we know the final empty spot must house the final missing letter, F.
The only part of this explanation I did not follow at first was how the puzzle could be solved without using the word FIR as a clue. I create these puzzles manually, which can take up to a couple of hours. Then I check that there is exactly one solution using a C program, which I wrote myself. As part of this process, I remove each word and only retain it as a clue if it is required to produce a unique solution. I had forgotten that my program checks that every letter from A to Y is included at least once in the clues. If there are any missing letters, the program halts tidily and does not proceed to look for a unique solution. I may now decide to change it so that it allows a maximum of one missing letter in the clues then places that letter at the end if there is only one place it can go.
It would be good to know what the Evening Standard does for their own gogen puzzles but unfortunately they never answer when I write to them. I may just have to go to London for a few days to collect some copies of the Evening Standard and try out their gogen puzzles again myself.
