Having reached 50, worker lives in fantasy land (8)
I believe the answer is:
atlantis
'fantasy land' is the definition.
The definition suggests a singular noun which matches the answer.
'having reached 50 worker lives' is the wordplay.
I cannot quite understand how this works, but
'50' could be 'l' (roman numeral) and 'l' is found in the answer.
'worker' could be 'ant' (worker is a type of ant) and 'ant' is present in the answer.
'lives' could be 'is' ('be' can be a synonym of 'live') and 'is' is located in the answer.
The remaining letters 'at' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
'in' acts as a link.
Can you help me to learn more?
(Other definitions for atlantis that I've seen before include "Catastrophic scene" , "In Greek legend, beautiful island submerged in the sea" , "Legendary sunken city" , "Lost island of Greek myth" , "Place of legend" .)