Individuals happy to leave pay-phones (4)
I believe the answer is:
ones
'individuals' is the definition.
(I've seen this before)
'happy to leave pay-phones' is the wordplay.
'to leave' is a deletion indicator.
'pay'+'phones'='payphones'
'payphones' with 'happy' taken out is 'ONES'.
(Other definitions for ones that I've seen before include "Individuals" , "Singles" , "Singletons" , "Aces" , "(Of ship) returning to port of origin" .)