Clever sailor joins the French (4)
I believe the answer is:
able
'clever' is the definition.
(able can mean skilled or talented)
'sailor joins the french' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'joins' means one lot of letters go next to another.
'the french' becomes 'le' ('the' in French).
'ab'+'le'='ABLE'
(Other definitions for able that I've seen before include "displaying skill" , "Bale out, being competent" , "With the required capacities" , "Fully competent" , "- -bodied; - seaman" .)