Some witches and crawler in agreement (8)
I believe the answer is:
covenant
'agreement' is the definition.
(I know that covenant is a type of agreement)
'some witches and crawler' is the wordplay.
'some witches' becomes 'coven' (a coven is a group of witches).
'and' means one lot of letters go next to another.
'crawler' becomes 'ant' (an ant crawls).
'coven'+'ant'='COVENANT'
'in' acts as a link.
(Other definitions for covenant that I've seen before include "Concordat, compact" , "Pact" , "Formal agreement of contract" , "Binding contract" , "Contract made in a convent" .)