Agree to get less (8)
I believe the answer is:
contract
This clue might be a double definition.
'agree to' is the first definition.
(thesaurus)
'get less' is the second definition.
'contract' can be an answer for 'get' (synonyms). I am not certain of the 'less' bit.
Can you help me to learn more?
(Other definitions for contract that I've seen before include "Agree - get smaller" , "Arrangement to commit murder" , "Undertake" , "Pick up" , "Covenant" .)