Not fit to have a bit of fun properly (6)
I believe the answer is:
unwell
'have a bit of fun properly' is the definition.
I can't judge whether this defines the answer.
'not fit' is the wordplay.
'not' becomes 'un' (I've seen this in other clues).
'fit' becomes 'well' (associated in meaning).
'un'+'well'='UNWELL'
'to' is the link.
Can you help me to learn more?
(Other definitions for unwell that I've seen before include "funny" , "Quaintly amusing" , "Indisposed" , "Out of sorts" , "Poorly" .)