In the end, prefer to alert changes introduced by men (6,2,5)
I believe the answer is:
sooner or later
'in' is the definition.
Both the answer and definition are adverbs. Perhaps they are linked in a way I don't understand?
'end prefer to alert changes introduced by men' is the wordplay.
'end' indicates one should take the final letters.
'changes' indicates an anagram.
'introduced by' is an insertion indicator (some letters introduce others into them).
'men' becomes 'sooner' (I can't justify this - if you can you should believe this answer much more).
The last letters of 'prefer to' are 'ro'.
'ro'+'alert'='roalert'
'roalert' with letters rearranged gives 'rorlate'.
'rorlate' inserted into 'sooner' is 'SOONER OR LATER'.
'the' is the link.
Can you help me to learn more?
(Other definitions for sooner or later that I've seen before include "not on the dot" , "Errors (a lot) one corrected, eventually" , "At some point" , "offering alternative times" , "Inevitably" .)