Support scruffy modern teens (11)
I believe the answer is:
endorsement
'support' is the definition.
(I know that endorsement is a type of support)
'scruffy modern teens' is the wordplay.
'scruffy' indicates anagramming the letters.
'modern'+'teens'='modernteens'
'modernteens' with letters rearranged gives 'ENDORSEMENT'.
(Other definitions for endorsement that I've seen before include "Support and approval" , "Want backing" , "okay?" , "Note on a driving licence" , "Official sanction or approval" .)