Boxing a long time, clobber despicable people (7)
I believe the answer is:
toerags
'despicable people' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'boxing a long time clobber' is the wordplay.
'boxing' is an insertion indicator ('box' can mean contain, as in to put in a box).
'a long time' becomes 'era' (a long period of time).
'clobber' becomes 'togs' (I can't justify this - if you can you should give a lot more credence to this answer).
'era' going into 'togs' is 'TOERAGS'.
Can you help me to learn more?
(Other definitions for toerags that I've seen before include "Wretched folk" , "Bums" , "Unpleasant people" .)