Instrument battery is old (5)

I believe the answer is:

cello

I'm a little stuck... Click here to teach me more about this clue!

'instrument' is the definition.
(cello is a kind of instrument)

'battery is old' is the wordplay.
'battery' becomes 'cell' (I can't justify this - if you can you should believe this answer much more).
'is old' becomes 'o' (common abbreviation eg in OE for Old English).
'cell'+'o'='CELLO'

Can you help me to learn more?

(Other definitions for cello that I've seen before include "Music-maker" , "Bass stringed instrument" , "String quartet instrument" , "Musical instrument like large violin held between knees" , "large-scale fiddle" .)

I've seen this clue in The Hindu.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.