Keen on catching start of record, the first few bars (5)
I believe the answer is:
intro
'the first few bars' is the definition.
(I've seen this before)
'keen on catching start of record' is the wordplay.
'keen on' becomes 'into' (I've seen this before).
'catching' indicates putting letters inside.
'start of' suggests taking the first letters.
The initial letter of 'record' is 'r'.
'into' enclosing 'r' is 'INTRO'.
(Other definitions for intro that I've seen before include "Beginning (colloq.)" , "Musical opening" , "Preliminary part" , "Beginning (informal)" , "Opener" .)