Subject of female performance is prosaic (6-2-4)
I believe the answer is:
matter-of-fact
'prosaic' is the definition.
(I know that prosaic can be written as matter-of-fact)
'subject of female performance' is the wordplay.
'subject' becomes 'matter' (synonyms).
'female' becomes 'f' (common abbreviation).
'performance' becomes 'act' (act is a kind of performance).
'matter'+'of'+'f'+'act'='MATTER-OF-FACT'
'is' is the link.
(Other definitions for matter-of-fact that I've seen before include "Unimaginative, emotionless" , "Straightforward and unemotional" , "Down to earth" , "Commonplace" , "Unemotional and practical" .)