Flawless French oddly cheeky to conceal (7)
I believe the answer is:
perfect
'flawless' is the definition.
('perfect' can be similar in meaning to 'flawless')
'french oddly cheeky to conceal' is the wordplay.
'oddly' means one should take alternating letters.
'cheeky' becomes 'pert' (I've seen this before).
'to conceal' means one lot of letters goes inside another.
The alternate letters of 'french' are 'fec'.
'fec' put inside 'pert' is 'PERFECT'.
(Other definitions for perfect that I've seen before include "Ideal, flawless" , "Flawless - finish" , "Complete" , "Getting by scheming" , "Faultless" .)