Bachelor boy's bundles (5)
I believe the answer is:
bales
'bundles' is the definition.
(bale is a kind of bundle)
'bachelor boy's' is the wordplay.
I cannot quite see how this works, but
'bachelor' could be 'ba' (abbreviation for Bachelor of Arts degree) and 'ba' is found in the answer.
'boy' could be 'les' (short for Leslie) and 'les' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for bales that I've seen is " 'Large bundles, of hay perhaps (5)'".)