Very hot in April and Oct. unusually (8)
I believe the answer is:
tropical
'very hot' is the definition.
(I've seen this before)
'april and oct unusually' is the wordplay.
'and' is a charade indicator (letters next to each other).
'unusually' indicates an anagram.
'april'+'oct'='apriloct'
'apriloct' with letters rearranged gives 'TROPICAL'.
'in' is the link.
(Other definitions for tropical that I've seen before include "Originating from hotter parts of the earth" , "Hot and humid, as north and south of the equator" , "Relating to hot and humid parts" , "Found in Cancer or Capricorn" , "Middle-earth" .)