Mature person of modern times, having some faults (5)
I believe the answer is:
adult
'mature person' is the definition.
(I've seen this in another clue)
'modern times having some faults' is the wordplay.
'modern times' becomes 'AD' (AD, Anno Domini, as opposed to BC, Before Christ).
'having' says to put letters next to each other.
'some faults' becomes 'ult' (I am not sure about this - if you are sure you should believe this answer much more).
'ad'+'ult'='ADULT'
'of' is the link.
Can you help me to learn more?
(Other definitions for adult that I've seen before include "No child" , "Person of mature age" , "Mature, fully grown" , "Indecent" , "(Of an animal) fully developed" .)