Spend about a pound for amusement (4)
I believe the answer is:
play
'amusement' is the definition.
(I know that play is a type of game of chance)
'spend about a pound' is the wordplay.
'spend' becomes 'pay' (I am not sure about this - if you are sure you should believe this answer much more).
'about' is an insertion indicator.
'a pound' becomes 'L' (abbreviation e.g. Lsd - pounds, shillings, pence).
'pay' enclosing 'l' is 'PLAY'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for play that I've seen before include "Amuse oneself - drama" , "stage production" , "See 17" , "Recreation" , "Slack - performance" .)