Make an application, or joke about it, possibly (3,2)
I believe the answer is:
put in
'make an application' is the definition.
'put in' can be an answer for 'make' (thesaurus). I'm not sure about the 'an application' bit.
'joke about it possibly' is the wordplay.
'joke' becomes 'pun' (pun is a type of joke).
'about' means one lot of letters goes inside another.
'possibly' is an anagram indicator.
'it' with letters rearranged gives 'ti'.
'pun' going around 'ti' is 'PUT-IN'.
'or' acts as a link.
Can you help me to learn more?
(Other definitions for put in that I've seen before include "Rugby throw to a set scrum" , "being asked to bat" , "Insert" , "Russian president" , "Submit" .)