Other ranks trapped by river in spate (7)
I believe the answer is:
torrent
'spate' is the definition.
(I know that torrent is a type of spate)
'other ranks trapped by river' is the wordplay.
'other ranks' becomes 'or' (military abbreviation).
'trapped by' means one lot of letters goes inside another.
'river' becomes 'trent' (River Trent).
'or' inserted inside 'trent' is 'TORRENT'.
'in' is the link.
(Other definitions for torrent that I've seen before include "Raging flow" , "Rushing stream, flood" , "Turbulent flow" , "Heavy stream" , "Swift or violent stream" .)