Understands right to wear pants (6)
I believe the answer is:
grasps
'understands' is the definition.
(grasping is a kind of understanding)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for grasps that I've seen before include "Clutches" , "Gets hold of" , "Takes firm grip of" , "Understands" , "Takes hold of firmly" .)