Forthright, vigorous (9)
I believe the answer is:
trenchant
I believe this is a double definition.
'forthright' is the first definition.
(I've seen this before)
'vigorous' is the second definition.
(synonyms)
(Other definitions for trenchant that I've seen before include "Fierce" , "Expressively incisive" , "Clear" , "Incisive in expression" , "Vigorous, incisive" .)