Leader placed cans (7)
I believe the answer is:
headset
'cans' is the definition.
(I've seen this before)
'leader placed' is the wordplay.
'leader' becomes 'head' (head is a kind of leader).
'placed' becomes 'set' (synonyms).
'head'+'set'='HEADSET'
(Other definitions for headset that I've seen before include "phones" , "Bicycle front bearing assembly" , "Radio operator's equipt." , "Assistance for listener" , "communications gear" .)