Corps given permission to split up (6)
I believe the answer is:
cleave
'split up' is the definition.
(cleave can mean to split in two)
'corps given permission' is the wordplay.
'corps' becomes 'C' (military abbreviation for corps).
'given' says to put letters next to each other.
'permission' becomes 'leave' (leave is a kind of permission).
'c'+'leave'='CLEAVE'
'to' is the link.
(Other definitions for cleave that I've seen before include "Adhere or split apart" , "Divide by chopping, or cling" , "Join or split" , "Chop or stick to" , "Unite together; split apart" .)