Flag, out of lust and ardour (8)
I believe the answer is:
standard
'flag' is the definition.
(standard is a kind of flag)
'out of lust and ardour' is the wordplay.
'out of' indicates the answer is hidden within the clue.
'STANDARD' can be found hidden inside 'lust and ardour'.
(Other definitions for standard that I've seen before include "Flag - norm" , "Guide-line" , "authority" , "Criterion, touchstone" , "type of flag" .)