Messy, silly one razed heater in the centre (8)
I believe the answer is:
slovenly
'messy' is the definition.
(thesaurus)
'silly one razed heater in the centre' is the wordplay.
I cannot quite understand how this works, but
'heater' could be 'oven' (I've seen this in another clue) and 'oven' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for slovenly that I've seen before include "Dirty and slipshod" , "Untidy, dirty" , "Habitually dirty and unkempt" , "Untidy, unkempt" , "Disorganised" .)