"Periods on horseback"

This is a reversal clue - look for indicators like 'back', 'returned', 'up' (in down clues), or 'west' (in across clues)

Join the wordplay parts together in sequence

Answer: CHUKKAS | Definition: 'Periods on horseback' | Wordplay: UK=”British” + K (King); into CHAS (informal for ‘Charles’, name of the current king)