Gull-ish behind? (6)
I believe the answer is:
astern
'behind?' is the definition.
(at the back or behind of a ship)
'gull-ish' is the wordplay.
I cannot quite see how this works, but
'gull' could be 'tern' (I've seen this in another clue) and 'tern' is found within the answer.
The remaining letters 'as' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for astern that I've seen before include "Toward the tail of a vessel" , "following behind vessel" , "Towards a ship's rear" , "Behind (naut.)" , "Backward" .)