Friendly French mate, captain, very competent (8)
I believe the answer is:
amicable
'friendly' is the definition.
(similar in meaning)
'french mate captain very competent' is the wordplay.
I cannot quite understand how this works, but
'competent' could be 'able' (similar in meaning) and 'able' is found in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for amicable that I've seen before include "Civil" , "warm" , "Easy to approach" , "In friendly spirit" , "Of friendly and affable disposition" .)