Blade caused girl to fetch plaster? (7)
I believe the answer is:
cutlass
'blade' is the definition.
(I know that Cutlass is a type of blade)
'girl to fetch plaster?' is the wordplay.
'girl' becomes 'lass' (lass can informally mean a girl).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'fetch plaster?' becomes 'cut' (I can't justify this - if you can you should give a lot more credence to this answer).
'lass' put after 'cut' is 'CUTLASS'.
'caused' is the link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for cutlass that I've seen before include "Piratical sword" , "What Blackbeard wielded" , "Sailor's blade" , "Curved sailors' sword" , "Short, broad-bladed sword" .)