Metalworker, terribly hit and miss, is dismissed (5)
I believe the answer is:
smith
'metalworker' is the definition.
(synonyms)
'terribly hit and miss is dismissed' is the wordplay.
'terribly' is an anagram indicator.
'and' is a charade indicator (letters next to each other).
'dismissed' suggests deleting specific letters.
'hit' after 'miss' is 'misshit'.
'misshit' with 'is' removed is 'mshit'.
'mshit' is an anagram of 'SMITH'.
(Other definitions for smith that I've seen before include "Person who makes things in metal, may be black" , "Common English surname" , "Forger" , "Worker in forge" , "Bessie - - , blues singer" .)