Have doubts about cult grabbing American power (7)
I believe the answer is:
suspect
'have doubts about' is the definition.
(I've seen this before)
'cult grabbing american power' is the wordplay.
'cult' becomes 'sect' (I've seen this before).
'grabbing' indicates putting letters inside.
'american' becomes 'us'.
'power' becomes 'p'.
'us'+'p'='usp'
'sect' enclosing 'usp' is 'SUSPECT'.
(Other definitions for suspect that I've seen before include "One is believed to be guilty but without proof" , "Consider or believe likely" , "Fishy" , "Doubt; mistrust" , "Funny" .)