First course at public house is sent back - it's not for a vegetarian or for a pescatarian to eat

'a vegetarian or for a pescatarian to eat' is the definition.
I can't tell whether this defines the answer.

'first course at public house is sent back it's not' is the wordplay.
'first' says to take the initial letters.
'at' is a charade indicator (letters next to each other).
'public house' becomes 'bar' (I've seen this before).
'is sent back' says the letters should be written in reverse.
'it's not' becomes 'meat' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The initial letter of 'course' is 'c'.
'bar' in reverse letter order is 'rab'.
'c'+'rab'+'meat'='CRABMEAT'

'for' acts as a link.

Can you help me to learn more?