Is said to be permissive with Latvians (5)
I believe the answer is:
letts
'latvians' is the definition.
(I've seen this in another clue)
'is said to be permissive' is the wordplay.
'is said' becomes 'ts' (I can't justify this - if you can you should believe this answer much more).
'to' says to put letters next to each other (I've seen this in other clues).
'be permissive' becomes 'let' (I've seen this in another clue).
'ts' after 'let' is 'LETTS'.
'with' is the link.
Can you help me to learn more?
I've seen this clue in the Evening Standard.
Want a hint initially instead of a full solution?
Install my app