Direction from Avon or Thames (5)
I believe the answer is:
north
'direction' is the definition.
(compass direction)
'from avon or thames' is the wordplay.
'from' indicates a hidden word.
'NORTH' can be found hidden inside 'avon or thames'.
(Other definitions for north that I've seen before include "A quarter" , "coming up from Brighton?" , "Lord -, PM; bearing" , "He let America go" , "Compass bearing" .)