Waters garden bordering river in curved shape (9)
I believe the answer is:
horseshoe
'curved shape' is the definition.
(a horseshoe is curved shape)
'waters garden bordering river' is the wordplay.
'waters' becomes 'hoses' (e.g. flowers).
'garden' becomes 'hoe' (to garden could mean to hoe).
'bordering' indicates putting letters inside.
'river' becomes 'r' (abbreviation for river).
'hoses'+'hoe'='hoseshoe'
'hoseshoe' going around 'r' is 'HORSESHOE'.
'in' is the link.
(Other definitions for horseshoe that I've seen before include "Crab" , "Plate nailed to equine hoof" , "in cavalry - one reduces friction" , "One could be lucky" , "Lucky sign" .)