Did butterfly start to pollute bog? (5)

I believe the answer is:

swamp

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'bog?' is the definition.
(I've seen this before)

'did butterfly start to pollute' is the wordplay.
'did butterfly' becomes 'swam' (I can't explain this - if you can you should believe this answer much more).
'start to' suggests taking the first letters.
The initial letter of 'pollute' is 'p'.
'swam'+'p'='SWAMP'

Can you help me to learn more?

(Other definitions for swamp that I've seen before include "Overwhelm; wetland" , "Seasonally-flooded lowland" , "Bog; inundate" , "In flood" , "Marshy land" .)

I've seen this clue in The Independent.

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