Delight plays part by river (7)
I believe the answer is:
rapture
'delight' is the definition.
(thesaurus)
'plays part by river' is the wordplay.
'plays' is an anagram indicator.
'by' is a charade indicator (letters next to each other).
'river' becomes 'ure' (I have seen 'River of Wensleydale ' mean 'ure' so perhaps 'river' could also mean 'ure'**).
'part' is an anagram of 'rapt'.
'rapt'+'ure'='RAPTURE'
(Other definitions for rapture that I've seen before include "Bliss, intense delight" , "Sheer bliss or ecstasy" , "Extreme delight" , "Ecstasy, seventh heaven" , "Intense joy" .)