Small wave tapped in source of water (9)
I believe the answer is:
standpipe
'source of water' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'small wave tapped in' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'wave' indicates anagramming the letters (I've seen 'waving' mean this (letters wave around)).
'tapped'+'in'='tappedin'
'tappedin' with letters rearranged gives 'tandpipe'.
's'+'tandpipe'='STANDPIPE'
Can you help me to learn more?
(Other definitions for standpipe that I've seen before include "Emergency source of water" , "Emergency water supply" , "Source of water during shortage" , "main conduit in emergencies?" , "temporary feed" .)