Crusty thing, the poet, Holder (8)
I believe the answer is:
scabbard
'holder' is the definition.
(I've seen this before)
'crusty thing the poet' is the wordplay.
'crusty thing' becomes 'scab' (I am not sure about this - if you are sure you should believe this answer much more).
'the poet' becomes 'bard' (bard is a kind of poet).
'scab'+'bard'='SCABBARD'
Can you help me to learn more?
(Other definitions for scabbard that I've seen before include "sword-carrier" , "place of weapon" , "foil container?" , "One holding a sword" , "You may see one holding a dagger" .)