Recommend a romantic partner to entertain very old Conservative (8)
I believe the answer is:
advocate
'recommend' is the definition.
('advocate' can be a synonym of 'recommend')
'a romantic partner to entertain very old conservative' is the wordplay.
'romantic partner' becomes 'date'.
'to entertain' indicates putting letters inside.
'very' becomes 'v' (abbreviation).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'conservative' becomes 'c' (abbreviation commonly used in UK politics).
'v'+'o'+'c'='voc'
'date' enclosing 'voc' is 'dvocate'.
'a'+'dvocate'='ADVOCATE'
(Other definitions for advocate that I've seen before include "Proponent" , "barman" , "Defender" , "One pleads a cause" , "Recommend - lawyer" .)