Flying uni flag could be worthwhile (7)
I believe the answer is:
gainful
'worthwhile' is the definition.
(thesaurus)
'flying uni flag' is the wordplay.
'flying' indicates an anagram.
'uni'+'flag'='uniflag'
'uniflag' with letters rearranged gives 'GAINFUL'.
'could be' is the link.
(Other definitions for gainful that I've seen before include "Bringing in money" , "Profitable and productive" .)