Mass survey, perhaps, upheld after swindle (6)
I believe the answer is:
dollop
'mass' is the definition.
(I have seen 'Shapeless mass ' mean 'dollop' so perhaps 'mass' could also mean 'dollop')
'survey perhaps upheld after swindle' is the wordplay.
'survey perhaps' becomes 'poll' (polling is a kind of surveying. I am not sure about the 'perhaps' bit.).
'upheld' says the letters should be written in reverse.
'after' is a charade indicator (letters next to each other).
'swindle' becomes 'do'.
'poll' backwards is 'llop'.
'llop' after 'do' is 'DOLLOP'.
Can you help me to learn more?
(Other definitions for dollop that I've seen before include "Semisolid lump" , "Squidgy lump (of food)" , "Small mass of eg cream" , "Large shapeless lump" , "Small, unmeasured amount" .)