Hot tip in essay (6)
I believe the answer is:
trendy
'hot' is the definition.
(I've seen this before)
'tip in essay' is the wordplay.
'tip' becomes 'end' (tip can mean the end of something).
'in' is an insertion indicator.
'essay' becomes 'try' (synonyms).
'end' going within '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" .)