Not professional, a struggling RU team (7)
I believe the answer is:
amateur
'not professional' is the definition.
('amateur' is the opposite to 'professional')
'a struggling ru team' is the wordplay.
'struggling' indicates anagramming the letters (I've seen this in other clues).
'ru'+'team'='ruteam'
'ruteam' is an anagram of 'mateur'.
'a'+'mateur'='AMATEUR'
(Other definitions for amateur that I've seen before include "Unpaid player" , "Dabbler" , "One who pursues an activity as a pastime only" , "Inept, non-professional" , "refusing payment" .)