Song that induces sleep (6)
I believe the answer is:
number
'song' is the definition.
(I've seen this in another clue)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for number that I've seen before include "less sensitive" , "more insensitive" , "(Symbol for) quantity" , "Mathematical value" , "Comparatively torpid" .)