In there Cthulhu's standing (5)
I believe the answer is:
erect
'standing' is the definition.
(similar in meaning)
'in there cthulhu's' is the wordplay.
'in' says the answer is hidden in the clue.
'ERECT' is hidden in the letters of 'there cthulhu'.
(Other definitions for erect that I've seen before include "Found" , "Construct, build" , "Upright or vertical" , "Standing vertically" , "Not having a list" .)