Spirit with look not OK -- ugh, awful! (5)
I believe the answer is:
ghoul
'spirit' is the definition.
(ghoul is a kind of spirit)
'look not ok ugh awful' is the wordplay.
'not' suggests deleting specific letters.
'awful' indicates an anagram.
'look' with 'ok' removed is 'lo'.
'lo'+'ugh'='lough'
'lough' with letters rearranged gives 'GHOUL'.
'with' acts as a link.
(Other definitions for ghoul that I've seen before include "Evil spirit alleged to feed on dead bodies" , "Spirit that robs graves and devours corpses" , "Morbid voyeur" , "Evil presence" , "Gruesome fiend" .)