Aware when tin OK to recycle (2,3,4)
I believe the answer is:
in the know
'aware' is the definition.
(I've seen this before)
'when tin ok to recycle' is the wordplay.
'to recycle' is an anagram indicator (use the letters again in a new way).
'when'+'tin'+'ok'='whentinok'
'whentinok' with letters rearranged gives 'IN THE KNOW'.
(Other definitions for in the know that I've seen before include "well-informed" , "Informally, having inside information" , "Aware" , "Having been informed" , "Possessing private information" .)