Pair upset by most woe (7)
I believe the answer is:
twosome
'pair' is the definition.
(twosome is a kind of pair)
'upset by most woe' is the wordplay.
'upset by' indicates anagramming the letters.
'most'+'woe'='mostwoe'
'mostwoe' anagrammed gives 'TWOSOME'.
(Other definitions for twosome that I've seen before include "match" , "Couple" , "Item" , "Pair, duo" , "game of golf" .)