Suspects party underlings blame the SNP's leaders (6)
I believe the answer is:
doubts
'suspects' is the definition.
('doubt' can be a synonym of 'suspect')
'party underlings blame the snp's leaders' is the wordplay.
'party' becomes 'do' (do can informally mean a party).
'leaders' says to take the initial letters.
The first letters of 'underlings blame the snp' is 'ubts'.
'do'+'ubts'='DOUBTS'
(Other definitions for doubts that I've seen before include "Isn't certain about, has reservations" , "Misgivings" , "Uncertainties" , "Thinks something unlikely" , "Suspicions" .)