Hold back beginning of precipitation and moisture (4)
I believe the answer is:
damp
'moisture' is the definition.
(I've seen this before)
'hold back beginning of precipitation' is the wordplay.
'hold back' becomes 'dam' (I've seen this in another clue).
'beginning of' indicates taking the first letters.
The first letter of 'precipitation' is 'p'.
'dam'+'p'='DAMP'
'and' acts as a link.
(Other definitions for damp that I've seen before include "Rising -, TV sitcom" , "Somewhat moist" , "soggy" , "A bit wet" , "dripping" .)