Employment for you and me a long time (5)
I believe the answer is:
usage
'employment' is the definition.
(synonyms)
'you and me a long time' is the wordplay.
'you and me' becomes 'us'.
'a long time' becomes 'age' (an age is a period of time).
'us'+'age'='USAGE'
'for' acts as a link.
(Other definitions for usage that I've seen before include "Style of language" , "phraseology" , "Usual practice" , "Acceptable language" , "Customary practice" .)