For example, Stan's in a nice mess! (8)
I believe the answer is:
instance
'for example' is the definition.
(synonyms)
'stan's in a nice mess' is the wordplay.
'in' indicates putting letters inside.
'mess' is an anagram indicator.
'nice' anagrammed gives 'ince'.
'stan' going inside 'ince' is 'INSTANCE'.
(Other definitions for instance that I've seen before include "Case in point" , "Example or single occurrence of something" , "Canniest (anag) - occurrence" , "Particular example" , "Case or example from ancients" .)