Husband, a royal, is quiet and severe (5)
I believe the answer is:
harsh
'severe' is the definition.
(I've seen this in another clue)
'husband a royal is quiet' is the wordplay.
'husband' becomes 'h' (abbreviation).
'royal' becomes 'r' (common abbreviation e.g. RM - Royal Marine).
'is quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'h'+'a'+'r'+'sh'='HARSH'
'and' is the link.
(Other definitions for harsh that I've seen before include "Strict, unfair" , "Unkind or cruel" , "Grating; severe" , "Punitive" , "Abrasive, rough or unkind" .)