Out of shape, you can still have fun with it (5)
I believe the answer is:
unfit
'out of shape' is the definition.
(out of shape can mean unfit or unhealthy)
'can still have fun with it' is the wordplay.
I cannot really understand how this works, but
an anagram of 'fun' is 'unf' which is within the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found in the answer.
A single letter 'i' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'you' is the link.
Can you help me to learn more?
(Other definitions for unfit that I've seen before include "Ill - out of shape" , "not worthy" , "Incapable" , "Inapt" , "Unsuitable" .)