Step in road when buggy backed (10)

I believe the answer is:

patronised

I'm a little stuck... Click here to teach me more about this clue!

'buggy backed' is the definition.
I can't tell whether this definition defines the answer.

'step in road' is the wordplay.
'step in road' anagrams to 'PATRONISED'.
However, I'm not clear how this is indicated.

'when' acts as a link.

Can you help me to learn more?

(Other definitions for patronised that I've seen before include "Frequented" , "Went regularly" , "Was customer" , "treated scornfully?" .)

I've seen this clue in The Telegraph.

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