London tourist attraction, one exerting a pull (5)
I believe the answer is:
tower
'london tourist' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'attraction one exerting a pull' is the wordplay.
I cannot really understand how this works, but
'pull' could be 'tow' (tow is a kind of pull) and 'tow' is located in the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tower that I've seen before include "Rise to great height" , "Skyscraper" , "Perhaps keep" , "Tall column" , "Rear" .)