Casually handles cooler porridge? (9)
I believe the answer is:
nicknames
'casually handles' is the definition.
'nicknames' can be an answer for 'handles' (I've seen this before). I am not certain of the 'casually' bit.
'cooler porridge?' is the wordplay.
'cooler' becomes 'nick' (I've seen this before).
'porridge?' becomes 'names' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'nick'+'names'='NICKNAMES'
Can you help me to learn more?
(Other definitions for nicknames that I've seen before include "Chalky and Shorty, for instance" , "sobriquets" , "Familiar or affectionate add-on appellations" , "Monikers" , "Handles" .)