Water thus rising further round end of garden? Wear this (10,4)
I believe the answer is:
wellington boot
'wear this' is the definition.
(I've seen this before)
'water thus rising further round end of garden?' is the wordplay.
'water thus rising' becomes 'welling' (water which is rising may be described as welling).
'further' becomes 'toboot' ('to boot' can mean 'further' or 'as well').
'round' indicates putting letters inside.
'end of' says to take the final letters.
The final letter of 'garden' is 'n'.
'toboot' placed around 'n' is 'tonboot'.
'welling'+'tonboot'='WELLINGTON BOOT'
(Another definition for wellington boot that I've seen is " Wear this".)