Visitors to Athens come across this (4)
I believe the answer is:
stoa
'this' is the definition.
The definition suggests a singular noun which matches the answer.
'visitors to athens come across' is the wordplay.
'across' says the answer is hidden in the clue.
'STOA' can be found hidden inside 'visitors to athens come'.
Can you help me to learn more?
(Other definitions for stoa that I've seen before include "Greek portico or colonnade" , "(In Ancient Greece) walkway with a roof supported by colonnades" , "Philosophers' porch" , "Make a Greek porch out of oats" , "Colonnade, covered walkway" .)