Memorised antler formation (6)
I believe the answer is:
learnt
'memorised' is the definition.
(to memorise is to learn by heart)
'antler formation' is the wordplay.
'formation' indicates anagramming the letters.
'antler' is an anagram of 'LEARNT'.
(Other definitions for learnt that I've seen before include "Realised" , "Committed to memory" , "Gained knowledge or skill" , "Came to know" , "Found out" .)