Doubt Ella taken in by smart arses (5,1,3)
I believe the answer is:
smell a rat
'doubt' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for smell a rat that I've seen before include "Detect something suspicious" , "Sense something is amiss" , "Have suspicion something is afoot" , "Sense something suspicious" , "Suspect trickery (colloq.)" .)