Search for water — amount round wicket (5)
I believe the answer is:
dowse
'search for water' is the definition.
(as in using a dowsing rod)
'amount round wicket' is the wordplay.
'amount' becomes 'dose' (dose is a kind of amount).
'round' is an insertion indicator.
'wicket' becomes 'w'.
'dose' placed around 'w' is 'DOWSE'.
(Other definitions for dowse that I've seen before include "Detect underground water" , "Use a divining rod" , "Search for water using hazel rod" , "put fire out" , "Prospect for water" .)