Smooth, starts to sing awfully, needling daughter (4)
I believe the answer is:
Here is my best explanation:
'smooth' is the definition.
(sanding is a kind of smoothing)
'starts to sing awfully needling daughter' is the subsidiary indication.
'starts to' suggests taking the first letters.
'daughter' becomes 'd'.
The first letters of 'sing awfully needling' is 'san'.
(Other definitions for sand that I've seen before include "woman writer Chopin loved", "Polish", "Fine stone particles", "Smooth with abrasive paper", "It's used to make glass", "Rock grains", "Seaside castle-building material", "Rock particles; smooth", "desert" and "Shore grain".)