Able to use either hand equally well (12)
I believe the answer is:
ambidextrous
'able to use either hand equally well' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ambidextrous that I've seen before include "Using both hands" , "Good with either hand" , "Equally skilful with either hand" , "Equally expert with both hands" , "Using either hand" .)