Limit referring to first pair of states — Rhode Island and Connecticut (8)
I believe the answer is:
restrict
'limit' is the definition.
(synonyms)
'referring to first pair of states rhode island and connecticut' is the wordplay.
'to first' suggests taking the first letters.
'pair of states' becomes 'est' (I am not sure about this - if you are sure you should believe this answer much more).
'rhode island' becomes 'ri' (US postal abbreviation).
'and' says to put letters next to each other.
'connecticut' becomes 'ct' (US postal abbreviation).
The first letter of 'referring' is 'r'.
'r'+'est'+'ri'+'ct'='RESTRICT'
(Other definitions for restrict that I've seen before include "Subject to limitations" , "'Restrain, limit (8)'" , "hamper" , "Limit, inhibit" , "Keep within bounds" .)