Spot cards (6)
I believe the answer is:
notice
'spot' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for notice that I've seen before include "warning to quit" , "'Take heed of, perceive (6)'" , "Instruction" , "Announcement or warning" , "Warning - proclamation" .)