Good luck symbol for a so-called crab (9)
I believe the answer is:
horseshoe
This could be a double definition.
'good luck symbol' is the first definition.
(I've seen this before)
'so-called crab' is the second definition.
'horseshoe' can be an answer for 'crab' (I've seen this before). I am not sure about the 'so-called' bit.
'for a' is the link.
Can you help me to learn more?
(Other definitions for horseshoe that I've seen before include "Steed's footwear" , "Supposedly lucky piece of metal" , "Good luck symbol" , "It's said to be lucky" , "Base metal forged" .)