Challenging in a deft fashion (7)
I believe the answer is:
defiant
'challenging' is the definition.
('defiant' can be similar in meaning to 'challenging')
'in a deft fashion' is the wordplay.
'fashion' indicates anagramming the letters.
'in'+'a'+'deft'='inadeft'
'inadeft' is an anagram of 'DEFIANT'.
(Other definitions for defiant that I've seen before include "Insubordinate" , "Open resistance" , "Mutinous" , "Openly resisting" , "Unyielding" .)