Mostly liable to go around one’s cage, perhaps (6)
I believe the answer is:
prison
'cage perhaps' is the definition.
(a cage could be a prison)
'mostly liable to go around one's' is the wordplay.
'mostly' means to remove the last letter (most but not all of the word).
'liable' becomes 'prone' (both can mean having a tendency for something).
'to go around' indicates putting letters inside.
'one's' becomes 'i's' (Roman numeral).
'prone' with its last letter taken off is 'pron'.
'pron' placed around 'is' is 'PRISON'.
(Other definitions for prison that I've seen before include "Penitentiary" , "Jail" , "Place of detention for criminals" , "Clink - jug" , "Gaol" .)