Concerning one normal check (4)
I believe the answer is:
rein
'check' is the definition.
(both can mean to control or limit)
'concerning one normal' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'one' becomes 'I' (Roman numeral).
'normal' becomes 'n' (this might be a standard abbreviation I've not previously seen).
're'+'i'+'n'='REIN'
Can you help me to learn more?
(Other definitions for rein that I've seen before include "Part of tack" , "Free ... is carte blanche" , "Strap on a bridle" , "Harness item" , "Hold back" .)