Exhausted after a day's shopping? (5)

I believe the answer is:

spent

I'm a little stuck... Click here to teach me more about this clue!

'exhausted' is the definition.
(similar in meaning)

I cannot understand how the rest of the clue works.

(Other definitions for spent that I've seen before include "Splashed out" , "Worn out - after shopping?" , "Worn Out, exhausted" , "Completely exhausted" , "Worn out, having laid out money" .)

I've seen this clue in The Globe and Mail.

Want a hint initially instead of a full solution? Install my app