Hot tip in essay (6)
I believe the answer is:
trendy
'hot' is the definition.
(I've seen this in another clue)
'tip in essay' is the wordplay.
'tip' becomes 'end' (tip can mean the end of something).
'in' means one lot of letters goes inside another.
'essay' becomes 'try' (synonyms).
'end' inserted inside 'try' is 'TRENDY'.
(Other definitions for trendy that I've seen before include "all the rage" , "Cool" , "With it, a la mode" , "In accordance with the latest fad" , "Modish" .)