*Tube, in London? (9)
(Another definition for tellingly that I've seen is " to good effect".)
'tube in london?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for telly that I've seen before include "'The box' (colloquial)" , "cop in seventies" , "One of the media" , "Familiar name for TV" , "The goggle-box" .)