Detectives in violent tussle seizing drug (7)
I believe the answer is:
sleuths
'detectives' is the definition.
(I know this)
'violent tussle seizing drug' is the wordplay.
'violent' indicates anagramming the letters.
'seizing' means one lot of letters goes inside another (inserted letters are seized).
'drug' becomes 'h' (H is an example).
'tussle' anagrammed gives 'sleuts'.
'sleuts' placed around 'h' is 'SLEUTHS'.
'in' acts as a link.
(Other definitions for sleuths that I've seen before include "Detectives" , "Private eyes" .)