Like many a roof, bound to be penetrated by hail ultimately (5)
I believe the answer is:
tiled
'like many a roof' is the definition.
'bound to be penetrated by hail ultimately' is the wordplay.
'bound' becomes 'tied' (I've seen this before).
'to be penetrated by' indicates putting letters inside (I've seen this in other clues).
'ultimately' indicates one should take the final letters.
The last letter of 'hail' is 'l'.
'tied' going around 'l' is 'TILED'.
(Other definitions for tiled that I've seen before include "with a glazed look" , "like bathrooms" , "Covered in ceramic slabs" , "Covered in pottery slabs" , "Lined with small glazed rectangles, say bathroom" .)