Learned about composer (4)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
arne
'composer' is the definition.
(I've seen this in other clues)
'learned about' is the wordplay.
'about' indicates a hidden word.
'ARNE' is hidden within 'learned'.
(Other definitions for arne that I've seen before include "Rule, Britannia author" , "Rule Britannia composer, d. 1778" , "Rule Britannia's composer, d. 1778" , "Thomas --, composer of Rule, Britannia!" .)