Become smaller and compact (8)
I believe the answer is:
contract
This clue is a double definition.
'become smaller' is the first definition.
(I've seen this before)
'compact' is the second definition.
('contract' can be a synonym of 'compact')
'and' is the link.
(Other definitions for contract that I've seen before include "Shrink in written agreement" , "Undertake" , "Agree - reduce" , "Promise" , "Covenant" .)