Shaping metal's important to him primarily (5)
I believe the answer is:
smith
'shaping metal's important to him primarily' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'metal's important to him primarily' is the wordplay.
'metal' becomes 'sm' (Sm is an example).
'primarily' says to take the initial letters.
The initial letters of 'important to him' is 'ith'.
'sm'+'ith'='SMITH'
(Other definitions for smith that I've seen before include "Worker in metals" , "Forger" , "Metal worker" , "Shoemaker" , "Worker in forge" .)