Constant pessimist has no yen for alfresco dining (6)
I believe the answer is:
picnic
'alfresco dining' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'constant pessimist has no yen' is the wordplay.
'constant' becomes 'pi' (mathematics: 3.14).
'pessimist' becomes 'cynic' (I've seen this in another clue).
'has no' suggests deleting specific letters.
'yen' becomes 'y' (resembles the symbol for the currency of Japan).
'cynic' with 'y' taken out is 'cnic'.
'pi'+'cnic'='PICNIC'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for picnic that I've seen before include "Informal meal in open air for pleasure" , "Informal meal taken in the open air" , "Take a meal outside" , "Easy task - outdoor event" , "Alfresco repast" .)