Starts to stroll through once awesome colonnade (4)
I believe the answer is:
stoa
'colonnade' is the definition.
(architectural term)
'starts to stroll through once awesome' is the wordplay.
'starts to' says to take the initial letters.
The initial letters of 'stroll through once awesome' is 'STOA'.
(Other definitions for stoa that I've seen before include "Ancient Greek portico" , "(In Ancient Greece) walkway with a roof supported by colonnades" , "Greek portico or colonnade" , "Zeno's place" , "It sheltered Greeks walking" .)