Grasp the little branch (4)
I believe the answer is:
twig
I believe this is a double definition.
'grasp' is the first definition.
(both can mean to realise something)
'little branch' is the second definition.
(I've seen this in another clue)
'the' is the link.
(Other definitions for twig that I've seen before include "Suddenly see; branchlet" , "Finally understand" , "Eventually grasp" , "Small tree shoot" , "very little from box, perhaps" .)