It falls slowly to begin with, at present (4)
I believe the answer is:
snow
'it falls' is the definition.
'slowly to begin with at present' is the wordplay.
'to begin with' indicates taking the first letters.
'at present' becomes 'now' ('now' can be a synonym of 'at present').
The first letter of 'slowly' is 's'.
's'+'now'='SNOW'
(Other definitions for snow that I've seen before include "Jon - - (Ch.4 News)" , "Basic White Christmas ingredient" , "Cold precipitation" , "White flakes" , "Downfall of white" .)