Right inside reorganised coal-pit it's very hot (8)
I believe the answer is:
tropical
'very hot' is the definition.
(in the tropics)
'right inside reorganised coal-pit' is the wordplay.
'right' becomes 'r' (common abbreviation).
'inside' is an insertion indicator.
'reorganised' indicates an anagram.
'coal'+'pit'='coalpit'
'coalpit' anagrammed gives 'topical'.
'r' placed within 'topical' is 'TROPICAL'.
'it's' acts as a link.
(Other definitions for tropical that I've seen before include "extremely warm" , "it could be too hot" , "April-Oct, unusually humid and very hot" , "Found in Cancer or Capricorn" , "Describes weather that is hot and humid" .)