Beginning to threaten song after the wee small hours? It must be the liqueur (3,5)
I believe the answer is:
tia maria
'the liqueur' is the definition.
(I've seen this before)
'beginning to threaten song after the wee small hours?' is the wordplay.
'beginning to' suggests taking the first letters.
'song' becomes 'aria' (piece of music in an opera).
'after' is a charade indicator (letters next to each other).
'the wee small hours?' becomes 'iam' (I can't justify this - if you can you should believe this answer much more).
The initial letter of 'threaten' is 't'.
'aria' after 'iam' is 'iamaria'.
't'+'iamaria'='TIA MARIA'
'it must be' is the link.
Can you help me to learn more?
(Other definitions for tia maria that I've seen before include "Coffee-flavoured trademarked liqueur" , "Coffee-flavour liqueur" , "Rum-based coffee liqueur" , "drink is served?" , "After-dinner liqueur" .)