Writer relies on this jocular title (3,4)
I believe the answer is:
his nibs
'this jocular title' is the definition.
'his nibs' can be an answer for 'title' (I have seen 'Mock title ' mean 'his nibs' so perhaps 'title' could also mean 'his nibs'). I'm unsure of the 'this jocular' bit.
'writer relies on' is the wordplay.
'writer' becomes 'nib' (something which writes).
'relies' becomes 'hiss' (I can't explain this - if you can you should give a lot more credence to this answer).
'on' indicates putting letters inside (as in clothing 'on' a person).
'nib' inserted within 'hiss' is 'HIS NIBS'.
Can you help me to learn more?
(Other definitions for his nibs that I've seen before include "used by a male author?" , "person plagued by pomposity" , "very important person" , "Mockingly, a pompous person" , "What writer may take care of" .)