Self-satisfaction felt when one sticks up location of monster (8)
I believe the answer is:
smugness
'self-satisfaction' is the definition.
(I know that smugness is a type of self-satisfaction)
'sticks up location of monster' is the wordplay.
'sticks' becomes 'gums'.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'location of monster' becomes 'ness' (I can't justify this - if you can you should believe this answer much more).
'gums' written backwards gives 'smug'.
'smug'+'ness'='SMUGNESS'
'felt when one' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Another definition for smugness that I've seen is " Excessive feeling of self-satisfaction".)