The most common and most likely answer to this crossword clue is the 6 letter word BLOWER
I've seen this crossword clue in The Guardian
B
L
O
W
E
R
More clues leading to the result BLOWER
Buddy explains!

The straight part
We know that "Phone" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case phone = blower.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 BLOWER mean?
BLOWER noun- A person who blows.
- Any device that blows.
- (usually preceded by the) Telephone.
- A ducted fan, usually part of a heating, ventilation, and/or air conditioning system.
- A braggart, or loud talker.
- The whale; so called by seamen, from its habit of spouting up a column of water.
- A small fish of the Atlantic coast, Sphoeroides maculatus; the puffer.