The most common and most likely answer to this crossword clue is the 4 plus 5 letter word FREE RANGE
I've seen this crossword clue in Independent
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More clues leading to the result FREE RANGE
Buddy explains!

The straight part
We know that "lacking a battery?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lacking a battery? = free range.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does FREE RANGE mean?
FREE RANGE adjective- Of, pertaining to, or produced by animals that are allowed to roam freely, rather than being confined indoors.
- Allowed to move about outdoors without supervision.