The most common and most likely answer to this crossword clue is the 6 plus 4 letter word MIDDLE NAME
I've seen this crossword clue in The Daily Telegraph
M
I
D
D
L
E
N
A
M
E
More clues leading to the result MIDDLE NAME
Buddy explains!
The straight part
We know that "Handle that may be used only occasionally?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case handle that may be used only occasionally? = middle name.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.