Came across husband in stays sporting jewels (9)
I believe the answer is:
amethysts
'jewels' is the definition.
(I know this)
'came across husband in stays sporting' is the wordplay.
'came across' becomes 'met' (to come across is to meet or encounter).
'husband' becomes 'h' (abbreviation).
'in' is an insertion indicator.
'sporting' indicates an anagram.
'met'+'h'='meth'
'stays' with letters rearranged gives 'aysts'.
'meth' going inside 'aysts' is 'AMETHYSTS'.
(Other definitions for amethysts that I've seen before include "Purple gemstones" , "Purple quartz stones" .)