Fish here in the middle refinery (7)
I believe the answer is:
smelter
'refinery' is the definition.
(I've seen this in another clue)
'fish here in the middle' is the wordplay.
'fish' becomes 'smelt' (smelt is a kind of fish).
'here in the middle' becomes 'er' (I can't explain this - if you can you should give a lot more credence to this answer).
'smelt'+'er'='SMELTER'
Can you help me to learn more?
(Other definitions for smelter that I've seen before include "Industrial plant for extracting metal by heat" , "One extracting metal from ore" , "Extractor of metal from ore" , "Industrial plan for extracting metals by heating" , "Place where metal is extracted from ore by heating" .)