Latvian allows husband to pen note (7)
I believe the answer is:
lettish
'latvian' is the definition.
(the Latvian language is also called Lettish)
'allows husband to pen note' is the wordplay.
'allows' becomes 'lets' ('let' can be a synonym of 'allow').
'husband' becomes 'h'.
'to pen' means one lot of letters goes inside another.
'note' becomes 'ti' (I've seen this in other clues).
'lets'+'h'='letsh'
'letsh' placed around 'ti' is 'LETTISH'.
(Other definitions for lettish that I've seen before include "East European" , "from the Baltic" , "Like some Europeans" , "foreign language" .)