Denied but obtains help (8)
I believe the answer is:
gainsaid
'denied' is the definition.
(to gainsay is to deny or dispute something)
'obtains help' is the wordplay.
'obtains' becomes 'gains' (gaining is a kind of obtaining).
'help' becomes 'aid' (synonyms).
'gains'+'aid'='GAINSAID'
'but' acts as a link.
(Other definitions for gainsaid that I've seen before include "Challenged" , "Formally denied or contradicted" .)