Hands round lead from informant and drug nark (4)
I believe the answer is:
rile
'nark' is the definition.
(I know that nark can be written as rile)
'hands round lead from informant and drug' is the wordplay.
'hands' becomes 'rl' (abbreviations for left and right).
'round' means one lot of letters goes inside another.
'lead from' suggests taking the first letters (the letter that leads the word).
'and' is a charade indicator (letters next to each other).
'drug' becomes 'e' (E is another name for ecstasy).
The initial letter of 'informant' is 'i'.
'rl' enclosing 'i' is 'ril'.
'ril'+'e'='RILE'
(Other definitions for rile that I've seen before include "Exasperate" , "Irritate considerably" , "Bother" , "Lire (anag)" , "'Vex, irritate (4)'" .)