Dropping fish without tail (4)
I believe the answer is:
skat
'dropping' is the definition.
(alternative spelling of scat)
'fish without tail' is the wordplay.
'fish' becomes 'skate' (skate is a kind of fish).
'without tail' means to remove the last letter.
'skate' with its last letter taken off is 'SKAT'.
(Other definitions for skat that I've seen before include "game of cards" , "dropping" , "Three-handed card game" .)