The most common and most likely answer to this crossword clue is the 7 letter word SPEAKER
I've seen this crossword clue in The Guardian
S
P
E
A
K
E
R
More clues leading to the result SPEAKER
- One calls to order audio equipment
- Lecturer parks jeep without bumpers badly
- 8, including top parliamentary official
- Vassal almost stealing crown, as chair of assembly
- Criminal keeps a revolver on either side of chair in house
- Central figure in Parliament, one declares
- Nazi carrying un-numbered rifle is the one in charge
- Presenter and what her voice may come from
Buddy explains!

The straight part
We know that "chair of assembly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case chair of assembly = speaker.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 SPEAKER mean?
SPEAKER noun- One who speaks.
- Loudspeaker.
- Speakerphone.
- The chair or presiding officer of certain legislative bodies, such as the U.K. House of Commons or the U.S. House of Representatives.
- One who makes a speech to an audience.
- A book containing passages of text for use in speeches.
- The producer of a given utterance (text, etc), whether actually spoken or e.g. written.
- A key on a woodwind instrument of the clarinet family (cf octave key on other instruments) which induces the instrument to overblow.