Yak it up (3)
I believe the answer is:
gab
'yak it up' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gab that I've seen before include "rabbit" , "The gift of the . . . is ability to talk fluently" , "Talk a lot" , "gossip" , "Natter" .)