Couple in Glasgow starts to notice ghastly local intonation (5)
I believe the answer is:
twang
'local intonation' is the definition.
(I've seen this before)
'couple in glasgow starts to notice ghastly' is the wordplay.
'couple in glasgow' becomes 'twa' (I can't justify this - if you can you should believe this answer much more).
'starts to' suggests taking the first letters.
The first letters of 'notice ghastly' is 'ng'.
'twa'+'ng'='TWANG'
Can you help me to learn more?
(Other definitions for twang that I've seen before include "Sound of elastic being plucked" , "Nasal quality - strumming noise" , "Plucking sound - nasal tone" , "nasal effect" , "Local accent" .)