When in-laws start bellyaching about every other thing, take a breath! (6)
I believe the answer is:
inhale
'take a breath' is the definition.
(inhaling is a kind of taking a breath)
'when in-laws start bellyaching about every other thing' is the wordplay.
I cannot really understand how this works, but
'when' could be 'e' (I've seen this in other clues) and 'e' is located in the answer.
'in' is found in the answer.
'about' could be 'a' (abbreviation in Chambers) and 'a' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for inhale that I've seen before include "take the air" , "Draw in air or smoke" , "Breathe in (gas, smoke)" , "Whiff" , "Draw breath" .)