Royal Highness popular round horned animal (5)
I believe the answer is:
rhino
'horned animal' is the definition.
(I've seen this before)
'royal highness popular round' is the wordplay.
'royal highness' becomes 'rh' (this might be a standard abbreviation I've not previously seen).
'popular' becomes 'in' (something that's 'in' is fashionable).
'round' becomes 'o' (round can mean a round object).
'rh'+'in'+'o'='RHINO'
Can you help me to learn more?
(Other definitions for rhino that I've seen before include "chargeable > 11 [LOLLY]?" , "Ready" , "endangered creature" , "Moola" , "Charging animal" .)