Gas providing heat, improving Newcastle area (6)
I believe the answer is:
ethane
'gas' is the definition.
(ethane is a gas)
'heat improving newcastle area' is the wordplay.
'improving' indicates anagramming the letters (letters must be sorted out or rectified).
'newcastle area' becomes 'ne' (abbreviation for North East).
'heat' anagrammed gives 'etha'.
'etha'+'ne'='ETHANE'
'providing' is the link.
(Other definitions for ethane that I've seen before include "Flammable gas; eat hen (anagram)" , "Ate hen (anag) - hydrocarbon gas" , "Flammable hydrocarbon" , "Compound" , "Chemical" .)