Look threatening in small hood (5)
I believe the answer is:
scowl
'look threatening' is the definition.
(I've seen this before)
'small hood' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'hood' becomes 'cowl' ('cowl' can be a synonym of 'hood').
's'+'cowl'='SCOWL'
'in' acts as a link.
(Other definitions for scowl that I've seen before include "Grimace" , "Angry frown" , "Look angry" , "Look threatening" , "Angrily frown" .)