Affected millions restricted by upper limit (4)
I believe the answer is:
camp
'affected' is the definition.
(camp can mean exaggerated or affected)
'millions restricted by upper limit' is the wordplay.
'millions' becomes 'm' (abbreviation).
'restricted by' indicates putting letters inside (inserted letters are restricted or trapped).
'upper limit' becomes 'cap' (I've seen this in another clue).
'm' placed within 'cap' is 'CAMP'.
(Other definitions for camp that I've seen before include "A tent, or effeminate in style" , "military depot" , "Affected, artificial" , "prehistoric site" , "Where erections are temporary" .)