The most common and most likely answer to this crossword clue is the 6 plus 6 letter word GLADYS COOPER
G
L
A
D
Y
S
C
O
O
P
E
R
Buddy explains!
The straight part
We know that "actress" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case actress = gladys cooper.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.