Run into bone in pit -- nasty (8)
I believe the answer is:
horrible
'nasty' is the definition.
(I've seen this before)
'run into bone in pit' is the wordplay.
'run into' becomes 'r' (I've seen this in other clues).
'bone' becomes 'rib' (rib is a type of bone).
'in' means one lot of letters goes inside another.
'pit' becomes 'hole' (a pit is a hole).
'r'+'rib'='rrib'
'rrib' placed within 'hole' is 'HORRIBLE'.
(Other definitions for horrible that I've seen before include "Appalling" , "Unpleasant, dreadful" , "'Ghastly, frightful (8)'" , "'Ghastly, grisly (8)'" , "Dreadful, awful" .)