Conceit revealing vitality in troubled times (7)
I believe the answer is:
egotism
'conceit' is the definition.
(I know that egotism is a type of conceit)
'vitality in troubled times' is the wordplay.
'vitality' becomes 'go' (I've seen this in other clues).
'in' means one lot of letters goes inside another.
'troubled' indicates anagramming the letters.
'times' is an anagram of 'etism'.
'go' inserted inside 'etism' is 'EGOTISM'.
'revealing' acts as a link.
(Other definitions for egotism that I've seen before include "Extreme self-conceit" , "Excessive absorbtion in oneself" , "self-regard" , "Self-centredness" , "Excessive conceit" .)