If upset and backward, somewhat doubtful (5)
I believe the answer is:
fishy
'somewhat doubtful' is the definition.
'fishy' can be an answer for 'doubtful' (thesaurus). I am unsure of the 'somewhat' bit.
'if upset and backward' is the wordplay.
'upset' says the letters should be written in reverse.
'and' says to put letters next to each other.
'backward' becomes 'shy' (I've seen this in another clue).
'if' reversed gives 'fi'.
'fi'+'shy'='FISHY'
Can you help me to learn more?
(Other definitions for fishy that I've seen before include "Questionable" , "Dodgy, suspicious" , "Suspicious, shady" , "As smelt, perhaps" , "Ray is so" .)