You'd expect to see him in the height of fashion (4)
I believe the answer is:
toff
'you'd expect to see him' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'in the height of fashion' is the wordplay.
'in' says the answer is hidden in the clue.
'TOFF' is hidden within 'height of fashion'.
Can you help me to learn more?
(Other definitions for toff that I've seen before include "Wealthy and well-dressed member of the upper classes" , "Posh type" , "Rich person (colloq.)" , "One could be stuck up" , "Posh chap" .)