Pros and cons explained succinctly at first (4)
I believe the answer is:
aces
'pros' is the definition.
(I've seen this in another clue)
'and cons explained succinctly at first' is the wordplay.
'at first' indicates taking the first letters.
The initial letters of 'and cons explained succinctly' is 'ACES'.
(Other definitions for aces that I've seen before include "Champions" , "Ones or elevens in cards" , "wartime pilots?" , "Two will make deuce" , "excellent service" .)