Lots up for integration (9)

I believe the answer is:

profusion

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'lots up' is the definition.
'profusion' can be an answer for 'lots' (I've seen this before). I'm not certain of the 'up' bit.

'for integration' is the wordplay.
'for' becomes 'pro' (as in being 'pro' something).
'integration' becomes 'fusion' (I can't justify this - if you can you should believe this answer much more).
'pro'+'fusion'='PROFUSION'

Can you help me to learn more?

(Other definitions for profusion that I've seen before include "Plenty" , "Abundance" , "Large number" , "Lots" .)

I've seen this clue in The Independent.

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