Gas trouble among sailors (5)
I believe the answer is:
radon
'gas' is the definition.
(I know that radon is a type of argonon)
'trouble among sailors' is the wordplay.
'trouble' becomes 'ado' (both can mean bother or commotion).
'among' means one lot of letters goes inside another.
'sailors' becomes 'RN' (abbreviation for Royal Navy).
'ado' inserted inside 'rn' is 'RADON'.
(Other definitions for radon that I've seen before include "Noble gas, Rn" , "Colourless gas, atomic number 86" , "Gaseous element, Rn" , "Rare noble gas" , "Element, symbol Rn" .)