The most common and most likely answer to this crossword clue is the 3 letter word ARM
I've seen this crossword clue in Independent
A
R
M
Buddy explains!

The straight part
We know that "Provide a piece" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case provide a piece = arm.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 ARM mean?
ARM noun- The portion of the upper human appendage, from the shoulder to the wrist and sometimes including the hand.
- The extended portion of the upper limb, from the shoulder to the elbow.
- A limb, or locomotive or prehensile organ, of an invertebrate animal.
- A long, narrow, more or less rigid part of an object extending from the main part or centre of the object, such as the arm of an armchair, a crane, a pair of spectacles or a pair of compasses.
- A bay or inlet off a main body of water.
- A branch of an organization.
- Power; might; strength; support.
- A pitcher
- One of the two parts of a chromosome.
- A group of patients in a medical trial.
- To take by the arm; to take up in one's arms.
- Poor; lacking in riches or wealth.
- To be pitied; pitiful; wretched.
- (usually used in the plural) A weapon.
- (in the plural) Heraldic bearings or insignia.
- (in the plural) War; hostilities; deeds or exploits of war.
- To supply with armour or (later especially) weapons.
- To prepare a tool or a weapon for action; to activate.
- To cover or furnish with a plate, or with whatever will add strength, force, security, or efficiency.
- To furnish with means of defence; to prepare for resistance; to fortify, in a moral sense.
- To take up weapons; to arm oneself.
- To fit (a magnet) with an armature.