Boast, stuffing rupees into sack (4)
I believe the answer is:
brag
'boast stuffing' is the definition.
'brag' can be an answer for 'boast' (synonyms). I'm unsure of the 'stuffing' bit.
'rupees into sack' is the wordplay.
'rupees' becomes 'r' (abbreviation for rupees).
'into' is an insertion indicator.
'sack' becomes 'bag' (I've seen this in another clue).
'r' put inside 'bag' is 'BRAG'.
Can you help me to learn more?
(Other definitions for brag that I've seen before include "Blow one's own trumpet" , "Boast about garb" , "game, making > boast" , "boast; form of poker" , "'Show off, boast (4)'" .)