Hot first of all in equatorial region, opposite then is cold (6)
I believe the answer is:
erotic
'hot' is the definition.
(both can mean sexy or sexual)
'first of all in equatorial region opposite then is cold' is the wordplay.
'first of all in' indicates taking the first letters.
'cold' becomes 'c' (eg on taps).
The initial letters of 'equatorial region opposite then is' is 'eroti'.
'eroti'+'c'='EROTIC'
(Other definitions for erotic that I've seen before include "love poem" , "Amatory" , "Conducive to arousing sexual desire" , "Relating to sexual desire" , "Carnal" .)