A bit of spadework reveals water (3)
I believe the answer is:
dew
'water' is the definition.
(dew is a kind of water)
'a bit of spadework reveals' is the wordplay.
'a bit of' says the answer is hidden in the clue (I've seen 'a bit' mean this (the answer is formed by a bit of the clue)).
'DEW' is hidden in the letters of 'spadework reveals'.
(Other definitions for dew that I've seen before include "Early freshness" , "Overnight condensation" , "Early-morning moisture" , "Moisture on ground" , "Early morning moisture" .)