By going soft at the end of November (3)
I believe the answer is:
per
'by' is the definition.
(I've seen this in another clue)
'going soft at the end of november' is the wordplay.
'going soft at' becomes 'pe' (I am not sure about this - if you are sure you should believe this answer much more).
'the end of' says to take the final letters.
The last letter of 'november' is 'r'.
'pe'+'r'='PER'
Can you help me to learn more?
(Other definitions for per that I've seen before include "According to" , "Preposition meaning for each" , "Preposition indicating by means of" , "For each or every" .)