The most common and most likely answer to this crossword clue is the 2 plus 4 plus 7 letter word AT ONES LEISURE
I've seen this crossword clue in The Times
A
T
O
N
E
S
L
E
I
S
U
R
E
Buddy explains!
The straight part
We know that "taking any amount of time" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case taking any amount of time = at ones leisure.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.