So blue after first love's gone off the boil (4)
I believe the answer is:
slow
'so blue' is the definition.
Both the answer and definition are adjectives. Perhaps there's a link between them I don't understand?
'first love's gone off the boil' is the wordplay.
I cannot quite see how this works, but
'first' could be 'low' (synonyms) and 'low' is found within the answer.
A single letter 's' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
'after' acts as a link.
Can you help me to learn more?
(Other definitions for slow that I've seen before include "Crawling" , "Taking a long time" , "Behind time" , "Leisurely" , "Lacking in pace or interest" .)