Nasty mix of fuels found around coalmine? (8)
I believe the answer is:
spiteful
'nasty' is the definition.
(similar in meaning)
'mix of fuels found around coalmine?' is the wordplay.
'mix of' indicates an anagram.
'found around' is an insertion indicator.
'coalmine?' becomes 'pit' (I've seen this before).
'fuels' is an anagram of 'seful'.
'seful' enclosing 'pit' is 'SPITEFUL'.
(Other definitions for spiteful that I've seen before include "Malevolent, wanting to hurt" , "Vindictive - malicious" , "With desire to hurt" , "Vengeful, malicious" , "nasty!" .)