Tool for fixing small drum support with unlimited junk (6,3)
I believe the answer is:
staple gun
'tool for fixing' is the definition.
(staple guns are used to fix things)
'small drum support with unlimited junk' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'drum' becomes 'tap' (both can mean to make a noise by hitting).
'support' becomes 'leg' (leg is a kind of support).
'with' means one lot of letters go next to another.
'unlimited' indicates the central letters (remove the limits/outer letters).
The middle letters of 'junk' are 'un'.
's'+'tap'+'leg'+'un'='STAPLE GUN'
(Other definitions for staple gun that I've seen before include "One that fires those fixing" , "Tool for inserting fasteners" .)