Hail falls in two directions on the roof (5)
I believe the answer is:
eaves
'roof' is the definition.
(thesaurus)
'hail falls in two directions on' is the wordplay.
'two directions' can mean two replacements for 'direction'.
'hail' becomes 'ave' (greeting in Latin).
'falls in' indicates putting letters inside.
'direction' becomes 's' (S is an example).
'direction' becomes 'e' (E is an example).
'on' means one lot of letters go next to another.
's' put after 'e' is 'es'.
'ave' going into 'es' is 'EAVES'.
'the' is the link.
(Other definitions for eaves that I've seen before include "parts of housetops" , "Section of roof" , "Overhanging part of roof" , "Overhanging roof edges" , "Overhanging edge of roof" .)