Urge to chuck teacher into the river (6)
I believe the answer is:
desire
'urge' is the definition.
(thesaurus)
'teacher into the river' is the wordplay.
'teacher' becomes 'sir' (a male teacher might be addressed as 'sir').
'into' indicates putting letters inside.
'the river' becomes 'dee' (River Dee).
'sir' put within 'dee' is 'DESIRE'.
'to chuck' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for desire that I've seen before include "Long for (something)" , "request" , "Strong need" , "Concupiscence" , "Reside (anag.)" .)