Stand by upright character entering temple (4)
I believe the answer is:
wait
'stand by' is the definition.
(I've seen this in another clue)
'upright character entering temple' is the wordplay.
'upright character' becomes 'I' (vertical letter of the alphabet).
'entering' indicates putting letters inside.
'temple' becomes 'wat' (type of Asian temple eg Angkor Wat).
'i' placed within 'wat' is 'WAIT'.
(Other definitions for wait that I've seen before include "Cool one's heels" , "Serve at table" , "Hold on" , "Be patient" , "Watchman" .)