Riders in Hackney tend to cycle for approval (11)
I believe the answer is:
endorsement
'for approval' is the definition.
(endorsement is a kind of approval)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for endorsement that I've seen before include "Note on a driving licence" , "okay?" , "Green light" , "Support and approval" , "Official sanction or approval" .)