Concert bootleg occasionally getting support (7)
I believe the answer is:
promote
'support' is the definition.
(I know that promote is a more specific form of the action support)
'concert bootleg occasionally getting' is the wordplay.
'concert' becomes 'prom' (abbreviation for promenade concert).
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
'getting' means one lot of letters go next to another.
The alternating letters of 'bootleg' are 'ote'.
'prom'+'ote'='PROMOTE'
(Other definitions for promote that I've seen before include "Contribute to progress or growth" , "Support, encourage" , "Raise to a more senior position" , "Encourage - upgrade" , "Advocate, advance" .)