Powerful, mighty (6)
I believe the answer is:
strong
I believe this clue is a double definition.
'powerful' is the first definition.
(associated in meaning)
'mighty' is the second definition.
(I've seen this before)
(Other definitions for strong that I've seen before include "Forceful" , "Potent" , "Resilient" , "Powerful; highly alcoholic" , "Able to withstand attack" .)