Heinrich, the hot-headed one (5)
I believe the answer is:
heine
'heinrich the hot-headed one' is the definition.
I can't tell whether this definition defines the answer.
'heinrich the hot-headed one' is the wordplay.
'heinrich' becomes 'he' (I can't explain this - if you can you should give a lot more credence to this answer).
'the hot' becomes 'in' (both can mean fashionable).
'headed' means to remove the first letter (head can mean to remove the top from something).
'one' becomes 'me' (a setter might use 'one' to humourously mean 'me').
'me' with its first letter taken away is 'e'.
'he'+'in'+'e'='HEINE'
Can you help me to learn more?
(Other definitions for heine that I've seen before include "Heinrich -, nineteenth century German poet" , "Heinrich -, Ger. poet" .)