River round York's centre in flood (7)
I believe the answer is:
torrent
'flood' is the definition.
(thesaurus)
'river round york's centre' is the wordplay.
'river' becomes 'trent' (I've seen this before**).
'round' is an insertion indicator.
'centre' indicates the central letters.
The middle of 'york' is 'or'.
'trent' going around 'or' is 'TORRENT'.
'in' acts as a link.
(Other definitions for torrent that I've seen before include "Turbulent flow" , "Raging flood" , "Overwhelming deluge" , "Strong stream" , "A rushing stream of water" .)