The process of understanding what's raised for Revenue (6)

I believe the answer is:

uptake

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'the process' is the definition.
(uptake is a kind of process)

'raised for revenue' is the wordplay.
'raised' becomes 'up' ('up' can be similar in meaning to 'raised').
'for revenue' becomes 'take' (I can't explain this - if you can you should believe this answer much more).
'up'+'take'='UPTAKE'

'of understanding what's' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.

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(Other definitions for uptake that I've seen before include "Acceptance of offer" , "Mental grasp" , "Apprehension" , "Ability to understand what is meant - some are slow on it" , "Comprehension" .)

I've seen this clue in the Irish Times.

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