Crew given fish as acknowledgment (9)
I believe the answer is:
handshake
'acknowledgment' is the definition.
(handshake is a kind of acknowledgment)
'crew given fish' is the wordplay.
'crew' becomes 'hands' (I've seen this before).
'given' means one lot of letters go next to another.
'fish' becomes 'hake' (hake is a kind of fish**).
'hands'+'hake'='HANDSHAKE'
'as' is the link.
(Other definitions for handshake that I've seen before include "Conventional sort of manual greeting" , "Conventional greeting of manual kind" , "Gesture of greeting or of agreeing a deal" , "introductory offer?" , "Physical greeting" .)