Keen on grabbing right start (5)
I believe the answer is:
intro
'start' is the definition.
(I've seen this before)
'keen on grabbing right' is the wordplay.
'keen on' becomes 'into' (I've seen this before).
'grabbing' means one lot of letters goes inside another.
'right' becomes 'r' (common abbreviation).
'into' going around 'r' is 'INTRO'.
(Other definitions for intro that I've seen before include "Beginning (colloq.)" , "Preliminary part" , "Song's opening" , "Jazz piece" , "Opening section" .)