Not favouring having sex endlessly around noon (4)
I believe the answer is:
anti
'not favouring' is the definition.
(I've seen this before)
'sex endlessly around noon' is the wordplay.
'sex endlessly' becomes 'ati' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'around' means one lot of letters goes inside another.
'noon' becomes 'n' (abbreviation).
'ati' going around 'n' is 'ANTI'.
'having' acts as a link.
Can you help me to learn more?
(Other definitions for anti that I've seen before include "Prefix meaning against" , "not favoured" , "Not in favor of" , "Person opposed" , "Definitely not pro" .)