Blah-blah-blah (3)
I believe the answer is:
'blah-blah-blah' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gab that I've seen before include "Talk, chatter (colloq.)" , "rabbit" , "Loquacity the gift of it" , "Talk at length, chatter" , "Natter" .)