Deny accepting outfit, oddly, but bargain (9)
I believe the answer is:
negotiate
'bargain' is the definition.
(thesaurus)
'deny accepting outfit oddly' is the wordplay.
'deny' becomes 'negate' (I've seen this before).
'accepting' indicates putting letters inside.
'oddly' indicates alternate letters.
The alternating letters of 'outfit' are 'oti'.
'negate' enclosing 'oti' is 'NEGOTIATE'.
'but' is the link.
(Other definitions for negotiate that I've seen before include "Discuss the terms of an arrangement" , "as diplomat does" , "Try to reach agreement through discussion" , "Find a way over (a difficult path)" , "Pass round" .)