Clutch; understand (5)
I believe the answer is:
grasp
This clue is a double definition.
'clutch' is the first definition.
(synonyms)
'understand' is the second definition.
(grasping is a kind of understanding)
(Other definitions for grasp that I've seen before include "Take hold of firmly" , "Seize, hold firmly" , "Hold firmly; understand" , "Catch on" , "Clutch" .)