Perfect foxtrot, riotous (8)
I believe the answer is:
flawless
'perfect' is the definition.
('flawless' can be similar in meaning to 'perfect')
'foxtrot riotous' is the wordplay.
I cannot quite see how this works, but
'foxtrot' could be 'f' (phonetic alphabet: alpha, bravo, charlie etc.) and 'f' is located in the answer.
The remaining letters 'lawless' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for flawless that I've seen before include "Pristine" , "Unblemished" , "Without blemish or fault" , "unimpaired" , "Without blemish, perfect" .)