This attained, perhaps, so can one get involved with female? (3,2,7)
I believe the answer is:
age of consent
'this attained' is the definition.
The definition suggests a singular noun which matches the answer.
'so can one get involved with female?' is the wordplay.
'involved with' indicates anagramming the letters (involved can mean confusing or complex).
'female?' becomes 'f' (common abbreviation).
'so'+'can'+'one'+'get'='socanoneget'
'socanoneget' anagrammed with 'f' makes 'AGE OF CONSENT'.
'perhaps' acts as a link.
(Other definitions for age of consent that I've seen before include "Legal majority?" , "Beyond which relations allowed" , "Time when agreement becomes legally valid" .)