This is an anagram - look for an indicator word that suggests mixing, rearranging, or playing around with letters.
The phrase 'to play' is your anagram indicator, telling you to rearrange the letters. Take the word 'LEARNT' and mix up all its letters to form a new word meaning horn.
Answer: ANTLER | 'To play' indicates an anagram of 'LEARNT' = ANTLER (a type of horn found on deer)