Simple course — tacos for starters (6)
I believe the answer is:
modest
'simple' is the definition.
(synonyms)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for modest that I've seen before include "Demure" , "self-effacing" , "Unassuming; limited" , "Unassuming; small" , "Humble, not pretentious or showy" .)