Circle area of water in reverse (4)
I believe the answer is:
loop
'circle area' is the definition.
'loop' can be an answer for 'circle' (looping is a kind of circling). I'm unsure of the 'area' bit.
'water in reverse' is the wordplay.
'water' becomes 'pool' (pool is a kind of water).
'in reverse' says the letters should be written backwards.
'pool' in reverse letter order is 'LOOP'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for loop that I've seen before include "ring road, say" , "Shape formed by a closed curve that does not intersect itself" , "not informed one's out of it" , "Curve that bends round and crosses itself" , "Aerobatics manoeuvre" .)