The most common and most likely answer to this crossword clue is the 6 letter word THELMA
I've seen this crossword clue in Financial Times
T
H
E
L
M
A
More clues leading to the result THELMA
- English and French articles about married woman
- Girl gets thanks when taking control
- Louise’s partner playing Hamlet
- Louise’s partner extremely tough male put out
- Louise’s friend cast in Hamlet
- Woman covering her head with strange metal
- Female arts graduate backing the learner
- and 20d make a buddy movie. Male is left out — he needs to regroup
Buddy explains!

The straight part
We know that "Louise’s partner" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case louise’s partner = thelma.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.