Bound to have become smaller (10)
I believe the answer is:
contracted
'bound' is the definition.
(thesaurus)
'become smaller' is the wordplay.
I cannot really understand how this works, but
'become smaller' could be 'contract' (I've seen this before) and 'contract' is present in the answer.
The remaining letters 'ed' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'to have' is the link.
Can you help me to learn more?
(Other definitions for contracted that I've seen before include "Formally agreed; shrank" , "Got shorter" .)