Blemish in difficult position to observe (4)
I believe the answer is:
spot
I believe this clue is a triple definition!
'blemish' is the first definition.
(I know that blemish can be written as spot)
'in' acts as a link.
'difficult position' is the second definition.
(a spot is a difficult or problematic situation)
'to observe' is the third definition.
(I've seen this in another clue)
(Other definitions for spot that I've seen before include "See; place" , "Notice; skin blemish" , "clock" , "Observe - place" , "[NIGHTCLUB]" .)