Carthaginian postcard about seat of learning (5)
I believe the answer is:
punic
'carthaginian' is the definition.
(synonyms)
'postcard about seat of learning' is the wordplay.
'postcard' becomes 'pc'.
'about' indicates putting letters inside.
'seat of learning' becomes 'uni' (I've seen this before).
'pc' placed around 'uni' is 'PUNIC'.
(Other definitions for punic that I've seen before include "Relating to Carthage" , "ancient language" , "Carthaginian" .)