Looking smart, are almost all in (7)
I believe the answer is:
staring
'looking' is the definition.
(staring is a kind of looking)
'smart are almost all in' is the wordplay.
'smart' becomes 'sting' (both can mean to burn or hurt).
'almost all' means to remove the last letter (most but not all of the word).
'in' indicates putting letters inside.
'are' with its last letter taken off is 'ar'.
'sting' enclosing 'ar' is 'STARING'.
(Other definitions for staring that I've seen before include "Gawking" , "Looking with fixed gaze" , "with eyes popping out" , "Gazing long and fixedly at" , "Looking fixedly" .)