Net's used to contain short temper (7)
I believe the answer is:
sweeten
'temper' is the definition.
(thesaurus)
'net's used to contain short' is the wordplay.
'used' indicates an anagram.
'to contain' is an insertion indicator.
'short' becomes 'wee' (I can't justify this - if you can you should believe this answer much more).
'nets' with letters rearranged gives 'sten'.
'sten' placed around 'wee' is 'SWEETEN'.
Can you help me to learn more?
(Other definitions for sweeten that I've seen before include "put in sugar" , "Add, eg, sugar to" , "Make more agreeable or acceptable" , "Appease" , "We teens! (anag)" .)