The most common and most likely answer to this crossword clue is the 11 letter word CANNIBALISE
I've seen this crossword clue in The Times
C
A
N
N
I
B
A
L
I
S
E
More clues leading to the result CANNIBALISE
Buddy explains!

The straight part
We know that "Use bits of" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case use bits of = cannibalise.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 CANNIBALISE mean?
CANNIBALISE verb- To eat (parts of) another of one's own species.
- To remove parts of (a machine, etc) for use in other similar machines.
- To reduce sales or market share (for one of one's own products) by introducing another.
- Rework old material; rehash.