Saying few words, the French Commander-in-Chief holding on (7)
I believe the answer is:
laconic
'saying few words' is the definition.
(laconic means not saying much)
'the french commander-in-chief holding on' is the wordplay.
'the french' becomes 'la' ('the' in French).
'commander-in-chief' becomes 'CIC' (abbreviation).
'holding' indicates putting letters inside.
'cic' enclosing 'on' is 'conic'.
'la'+'conic'='LACONIC'
(Other definitions for laconic that I've seen before include "Terse, brief of speech" , "Succinct in speech" , "Tersely spoken" , "'Curt, terse (7)'" , "In short" .)