As a treatment, it's right for one beset by bad pains (7)
I believe the answer is:
aspirin
'as a treatment' is the definition.
I can't judge whether this definition defines the answer.
'right for one beset by bad pains' is the wordplay.
'right' becomes 'r' (common abbreviation).
'for' says to put letters next to each other (I've seen this in other clues).
'one' becomes 'I' (Roman numeral).
'beset by' indicates putting letters inside ('beset' could historically mean 'cover').
'bad' indicates an anagram.
'r' put after 'i' is 'ir'.
'pains' is an anagram of 'aspin'.
'ir' going within 'aspin' is 'ASPIRIN'.
'it's' is the link.
Can you help me to learn more?
(Other definitions for aspirin that I've seen before include "Pain-relieving tablet" , "Common drug in Paris" , "Sip rain (anag.)" , "Anodyne" , "Pain relief" .)