Lurching drunk going around grass (7)
I believe the answer is:
tossing
'lurching' is the definition.
(thesaurus)
'drunk going around grass' is the wordplay.
'drunk' becomes 'sot' (both can mean someone who drinks too much).
'going around' says the letters should be written backwards.
'grass' becomes 'sing' (both can mean to act as an informant).
'sot' backwards is 'tos'.
'tos'+'sing'='TOSSING'
(Other definitions for tossing that I've seen before include "Flinging" , "'. . . . . . . the caber', Scottish sport" .)