Gains knowledge (6)
I believe the answer is:
learns
'gains knowledge' is the definition.
('learn' can be a synonym of 'gain knowledge')
This is the entire clue.
(Other definitions for learns that I've seen before include "Gains knowledge or skills" , "Gains knowledge or skill" , "Gains understanding from study or experience" , "Imbibes knowledge" , "Finds out" .)