Vigorously effective (9)
I believe the answer is:
trenchant
(Other definitions for trenchant that I've seen before include "biting" , "Showing keenness" , "Incisive in expression" , "Vigorous, incisive" , "Clear-cut and hard-hitting" .)
I believe the answer is:
trenchant
(Other definitions for trenchant that I've seen before include "biting" , "Showing keenness" , "Incisive in expression" , "Vigorous, incisive" , "Clear-cut and hard-hitting" .)