Intelligence shown by ponies about to mature (9)
I believe the answer is:
espionage
'intelligence' is the definition.
(espionage is a kind of intelligence)
'shown by ponies about to mature' is the wordplay.
'shown by' is a charade indicator (letters next to each other).
'about' is an anagram indicator.
'to mature' becomes 'age' ('age' can be a synonym of 'mature').
'ponies' with letters rearranged gives 'espion'.
'espion' next to 'age' is 'ESPIONAGE'.
(Other definitions for espionage that I've seen before include "undercover work" , "hush-hush work" , "intelligence" , "007's game" , "agent's job" .)