Flat ceramic includes date mark in Spanish (5)
I believe the answer is:
tilde
'mark in spanish' is the definition.
'tilde' can be an answer for 'mark' (tilde is a kind of mark). I am not sure about the 'in spanish' bit.
'flat ceramic includes date' is the wordplay.
'flat ceramic' becomes 'tile' (I've seen this in another clue. I am not sure about the 'flat' bit.).
'includes' means one lot of letters goes inside another.
'date' becomes 'd' (abbreviation e.g. dob - date of birth).
'tile' going around 'd' is 'TILDE'.
Can you help me to learn more?
(Other definitions for tilde that I've seen before include "Mark, sometimes on keyboards" , "Wavy line in Spanish" , "Diacritical sign over letter" , "Sign on Spanish character" , "Squiggly mark" .)