The most common and most likely answer to this crossword clue is the 6 letter word EXHALE
I've seen this crossword clue in The Times
E
X
H
A
L
E
More clues leading to the result EXHALE
- Discharge former partner in robust health
- Sound of body after divorcee gets discharge
- No longer healthy to produce emissions
- Puff, no longer fit?
- Puff perhaps, now apparently unhealthy?
- Puff away: not fit any more?
- Prince Henry in river having to breathe out
- No longer healthy to breathe out
- Old lover? Well, don’t hold your breath
- Cross punched into a heel designed to let air out
Buddy explains!

The straight part
We know that "to produce emissions" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case to produce emissions = exhale.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 EXHALE mean?
EXHALE noun- An exhalation.
- To expel air from the lungs through the nose or mouth by action of the diaphragm, to breathe out.
- To expel (something, such as tobacco smoke) from the lungs by action of the diaphragm.
- To pass off in the form of vapour; to emerge.
- To emit (a vapour, an odour, etc.).
- To draw out; to cause to be emitted in vapour.