Conservative and old Independent bath prepared to shack up together (7)
I believe the answer is:
cohabit
'shack up together' is the definition.
(to cohabit with someone is to live with them)
'conservative and old independent bath prepared' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'and' says to put letters next to each other.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'independent' becomes 'i'.
'prepared' indicates anagramming the letters.
'i'+'bath'='ibath'
'ibath' is an anagram of 'habit'.
'c'+'o'+'habit'='COHABIT'
'to' is the link.
(Other definitions for cohabit that I've seen before include "Live together as husband and wife" , "Live together as unmarried couple" , "Live together, married or not" , "16 ac 17 ac" , "Share residence" .)