Plentiful information on leader of union in love (8)
I believe the answer is:
generous
'plentiful' is the definition.
(thesaurus)
'information on leader of union in love' is the wordplay.
'information' becomes 'gen' (gen can informally mean information).
'on' indicates putting letters inside (as in clothing 'on' a person).
'leader of' indicates taking the first letters.
'in love' becomes 'eros' (I've seen this before).
The initial letter of 'union' is 'u'.
'u' inserted into 'eros' is 'erous'.
'gen'+'erous'='GENEROUS'
(Other definitions for generous that I've seen before include "Free" , "Lavish" , "Bountiful, unselfish" , "Willing to give unselfishly" , "Kind towards others" .)