Talent ineffectual for the most part (4)
I believe the answer is:
nous
'talent' is the definition.
(nous or common sense is a type of talent)
'ineffectual for the most part' is the wordplay.
'ineffectual' becomes 'no use' (I've seen this before).
'for the most part' means to remove the last letter (most but not all of the letters).
'nouse' with its last letter taken away is 'NOUS'.
(Other definitions for nous that I've seen before include "Savvy" , "We, in France, have common sense" , "Common sense (sl.)" , "FT in Paris, say" , "Sound practical judgement" .)