Bob upset a lady at the Nag's Head (5)

I believe the answer is:

dylan

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'bob' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

'upset a lady at the nag's head' is the wordplay.
'upset' is an anagram indicator.
'at' says to put letters next to each other.
'head' suggests taking the first letters.
The first letter of 'nags' is 'n'.
'lady' anagrammed gives 'dyla'.
'dyla'+'n'='DYLAN'

Can you help me to learn more?

(Other definitions for dylan that I've seen before include "Bob (singer-songwriter) - Thomas (poet)" , "and 19: Welsh poet" , "Bob (musician) or Thomas (poet)" , "Bob -, Blowin' in the Wind singer" , "... Thomas, Welsh writer" .)

I've seen this clue in the Evening Standard.

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