Praise hot drink ingested by youngsters in school (8)
I believe the answer is:
'praise' is the definition.
(flattery is a kind of praise)
'hot drink ingested by youngsters in school' is the wordplay.
'hot drink' becomes 'latte' (type of coffee).
'ingested by' indicates putting letters inside.
'youngsters in school' becomes 'fry' (young fish - a school is a group of fish).
'latte' placed into 'fry' is 'FLATTERY'.
(Other definitions for flattery that I've seen before include "It is said to get one nowhere" , "phony praise" , "Could it get you anywhere?" , "Felt tray (anag.)" , "Insincere praise (that will get you nowhere?)" .)