Lover, once clear, not entirely free (6)
I believe the answer is:
exempt
'entirely free' is the definition.
'exempt' can be an answer for 'free' (exempt can mean to free or release). I'm unsure of the 'entirely' bit.
'lover once clear not' is the wordplay.
'lover once' becomes 'ex' (an ex-lover).
'clear not' becomes 'empt' (I can't explain this - if you can you should believe this answer much more).
'ex'+'empt'='EXEMPT'
Can you help me to learn more?
(Other definitions for exempt that I've seen before include "let off the hook" , "Duty-free" , "Free from liability. excused" , "Not liable, as others may be" , "Not subject to, taxation perhaps" .)