Are within our rights to be less common (5)
I believe the answer is:
rarer
'be less common' is the definition.
('rare' can be the opposite of 'common' so perhaps 'rarer' is reasonable for 'less common')
'are within our rights' is the wordplay.
I cannot really understand how this works, but
'are' could be 'a' (short for 'are', historical unit of measurement) and 'a' is located in the answer.
'rights' could be 'rr' (two abbreviations for right) and 'rr' is present in the remaining letters.
The remaining letters 'er' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'to' is the link.
Can you help me to learn more?
(Other definitions for rarer that I've seen before include "steak may be wanted thus?" , "More unusual" , "less easy to find" , "even less common" , "Thinner" .)