Thus wasted month to secure memorable quickie! (7)
I believe the answer is:
thomson
'memorable quickie' is the definition.
The definition suggests a singular noun which matches the answer.
'thus wasted month to secure' is the wordplay.
'thus' becomes 'so' (synonyms).
'wasted' indicates anagramming the letters.
'to secure' is an insertion indicator (inserted letters are secured inside).
'month' is an anagram of 'thomn'.
'so' placed inside 'thomn' is 'THOMSON'.
Can you help me to learn more?
(Other definitions for thomson that I've seen before include "Virgil -, US composer" , "J.J. -, English physicist who discovered the electron" , "Kelvin" .)