Wrongly firing Minister without Portfolio at first (5)
I believe the answer is:
arson
'wrongly firing' is the definition.
(setting a building on fire)
'minister without portfolio at first' is the wordplay.
I cannot really see how this works, but
'at' could be 'on' (location) and 'on' is found in the answer.
'first' could be 'a' and 'a' is located in the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for arson that I've seen before include "Incendiary crime" , "Incendiary act" , "Malicious fire-raising" , "Malicious fire-lighting" , "Pyromaniac's crime" .)