Among the last up, I did look silly! (6)
I believe the answer is:
stupid
'silly' is the definition.
(I've seen this before)
'among the last up i did look' is the wordplay.
'among' says the answer is hidden in the clue.
'STUPID' can be found hidden inside 'last up i did look'.
(Other definitions for stupid that I've seen before include "Not intelligent, thick" , "Barmy" , "Without much intelligence" , "Senseless" , "Idiot" .)