Those filming great times on the river? (7)
I believe the answer is:
cameras
'those filming great' is the definition.
I can't tell whether this defines the answer.
'times on the river?' is the wordplay.
'times' becomes 'eras' (era is a kind of time).
'on' is a charade indicator (letters next to each other).
'the river?' becomes 'cam' (river in Cambridge, England).
'eras' after 'cam' is 'CAMERAS'.
Can you help me to learn more?
(Other definitions for cameras that I've seen before include "television equipment" , "Image recorders" , "Light-proof boxes" .)