The most common and most likely answer to this crossword clue is the 9 letter word LIFEGUARD
I've seen this crossword clue in The Daily Telegraph
L
I
F
E
G
U
A
R
D
Buddy explains!
The straight part
We know that "one’s occasionally needed when bathing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one’s occasionally needed when bathing = lifeguard.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.
What does LIFEGUARD mean?
LIFEGUARD noun- A bodyguard or unit of bodyguards, a guard of someone's (especially a king's) life or person.
- An attendant, usually an expert swimmer, employed to save swimmers in trouble or near drowning at a body of water.
- A lifesaver.
- A sturdy metal bracket fixed in front of each of the leading wheels of a train to deflect small objects away from the wheels to prevent derailment.