Omit sailor's fish (8)
I believe the answer is:
skipjack
'fish' is the definition.
(skipjack is a kind of fish)
'omit sailor's' is the wordplay.
'omit' becomes 'skip' (skipping is a kind of omiting).
'sailor' becomes 'jack' (informal term for a sailor).
'skip'+'jack'='SKIPJACK'
(Other definitions for skipjack that I've seen before include "Food fish" , "Type of tuna" , "sailing boat" .)