Charge the setter's applied to base of furnace (6)
I believe the answer is:
impute
'charge' is the definition.
(thesaurus)
'the setter's applied to base of furnace' is the wordplay.
'the setter's' becomes 'im' (I've seen this in other clues).
'applied to' becomes 'put' (I can't explain this - if you can you should give a lot more credence to this answer).
'base of' says to take the final letters.
The final letter of 'furnace' is 'e'.
'im'+'put'+'e'='IMPUTE'
Can you help me to learn more?
(Other definitions for impute that I've seen before include "Uptime (anag.)" , "'Attribute, assign (6)'" , "reckon" , "Attribute or credit to" , "Attribute (something bad) to someone" .)