Firm sort of date's not to eat (9)
I believe the answer is:
steadfast
'firm' is the definition.
(synonyms)
'sort of date's not to eat' is the wordplay.
I cannot really see how this works, but
an anagram of 'eat' is 'tea' which is located in the answer.
'date' could be 'd' (abbreviation e.g. dob - date of birth) and 'd' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for steadfast that I've seen before include "Constant; true" , "Resolutely firm" , "Dedicated" , "Firm, fixed and faithful" , "Firm and unwavering" .)