Last bit of this jaunt -- go on spending spree? (4)
I believe the answer is:
shop
'go on spending spree?' is the definition.
'last bit of this jaunt' is the wordplay.
'last bit of' indicates one should take the final letters.
'jaunt' becomes 'hop'.
The last letter of 'this' is 's'.
's'+'hop'='SHOP'
(Other definitions for shop that I've seen before include "Inform on (slang)" , "Emporium" , "Retail establishment" , "Betray - place selling things" , "Make purchase; inform on (someone)" .)