Clue: £25 premium on Nobu's yakitori starters (4)
Answer: PONY
Explanation: Definition: £25

**P**(remium) **O**(n) **N**(obu's) **Y**(akatori) [*starters*]
 

 
A pony is a slang term for £25, which is believed to have originated from a picture of a pony that featured on a 25 rupee note in 18th century, although other theories exist.