Optimist that is swallowing what’s periodically in tabloid (8)
I believe the answer is:
idealist
'optimist' is the definition.
(thesaurus)
'that is swallowing what's periodically in tabloid' is the wordplay.
'that is' becomes 'id est' ('that is' in Latin).
'swallowing' is an insertion indicator.
'what's periodically in tabloid' becomes 'ali' (I can't justify this - if you can you should give a lot more credence to this answer).
'idest' going around 'ali' is 'IDEALIST'.
Can you help me to learn more?
(Other definitions for idealist that I've seen before include "Visionary" , "Person with lofty and unselfish aspirations" , "Perfectionist" , "wishful thinker" , "One who aims for perfection, may be unrealistic" .)