It makes a straight line for the sovereign (5)
I believe the answer is:
ruler
'it' is the definition.
The definition suggests a singular noun which matches the answer.
'a straight line for the sovereign' is the wordplay.
'a straight line' becomes 'rule' (I've seen this in another clue).
'for' is a charade indicator (letters next to each other).
'the sovereign' becomes 'r' (abbreviation for rex or regina, king or queen).
'rule'+'r'='RULER'
'makes' acts as a link.
Can you help me to learn more?
(Other definitions for ruler that I've seen before include "provider of measured information" , "Queen maybe" , "Governor or drawing stick" , "Source of line" , "Man in charge" .)