As loaves go, this is a gem! (8)
I believe the answer is:
baguette
'gem' is the definition.
(I've seen this in another clue)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for baguette that I've seen before include "Bread roll" , "Long French breadstick" , "Long loaf - tube gate (anag)" , "Narrow French stick loaf" , "A long thin French loaf" .)