Swift to provide a market permit (7)
I believe the answer is:
martlet
'swift' is the definition.
(I've seen this before)
'a market permit' is the wordplay.
'a market' becomes 'mart' (synonyms).
'permit' becomes 'let' (synonyms).
'mart'+'let'='MARTLET'
'to provide' acts as a link.
(Other definitions for martlet that I've seen before include "Swallow (in heraldry)" , "Heraldic swallow" , "Heraldic bird" , "Charge, being legless" , "... once swift" .)