Good money given by member, tip included in change (5,6)
I believe the answer is:
legal tender
'good money' is the definition.
(I've seen this before)
'member tip included in change' is the wordplay.
'member' becomes 'leg' (leg is a kind of member).
'tip' becomes 'end'.
'included in' indicates putting letters inside.
'change' becomes 'alter' (synonyms).
'end' placed within 'alter' is 'altender'.
'leg'+'altender'='LEGAL TENDER'
'given by' acts as a link.
(Other definitions for legal tender that I've seen before include "Valid currency" , "... [HALF CROWNS] no longer this" , "Official currency" , "Good money" , "coins?" .)