North Warwickshire town where sister misplaced a note … (8)
I believe the answer is:
nuneaton
'north warwickshire town' is the definition.
(Nuneaton is a town in Warwickshire)
'sister misplaced a note' is the wordplay.
'sister' becomes 'nun' (sister is a term of address for a nun).
'misplaced' indicates anagramming the letters.
'a'+'note'='anote'
'anote' is an anagram of 'eaton'.
'nun'+'eaton'='NUNEATON'
'where' acts as a link.
(Other definitions for nuneaton that I've seen before include "midlands town" , "Warwickshire town" , "northern English town" .)