English teacher blocks new idea for hymn (4,4)
I believe the answer is:
dies irae
'hymn' is the definition.
(Dies Irae is an example)
'english teacher blocks new idea' is the wordplay.
'english' becomes 'e' (abbreviation).
'teacher' becomes 'sir' (I've seen this before).
'blocks' is an insertion indicator (the inside letters form a 'blockage').
'new' indicates an anagram.
'e'+'sir'='esir'
'idea' is an anagram of 'diae'.
'esir' inserted inside 'diae' is 'DIES IRAE'.
'for' is the link.
(Other definitions for dies irae that I've seen before include "Latin hymn (day of wrath)" , "when the Lord passes judgment?" , "Hymn featuring in a Requiem Mass" , "section of Requiem?" .)