The most common and most likely answer to this crossword clue is the 3 letter word SIT
I've seen this crossword clue in The Daily Telegraph
S
I
T
More clues leading to the result SIT
- Sort of bike offering exercise, with appeal
- Is turning up with Irish politician to have sort of meal?
- Exercise set: one’s somersaulting
- Model order for setter perhaps to settle
- Appearing in dungarees, Italian model
- Something wrong about Italian protest
- Strike is upsetting local community — 500 involved
- Relax, ’tis up the other way
- Become alert for crunch
- Overturned position is for exercise
Buddy explains!

The straight part
We know that "exercise" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case exercise = sit.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 SIT mean?
SIT noun- Subsidence of the roof of a coal mine.
- An event, usually lasting one full day or more, where the primary goal is to sit in meditation.
- (of a person) To be in a position in which the upper body is upright and supported by the buttocks.
- (of a person) To move oneself into such a position.
- (of an object) To occupy a given position permanently.
- To remain in a state of repose; to rest; to abide; to rest in any position or condition.
- To be a member of a deliberative body.
- Of a legislative or, especially, a judicial body such as a court, to be in session.
- To lie, rest, or bear; to press or weigh.
- To be adjusted; to fit.
- (of an agreement or arrangement) To be accepted or acceptable; to work.
- (causative) To cause to be seated or in a sitting posture; to furnish a seat to.
- To accommodate in seats; to seat.
- To babysit.
- To take, to undergo or complete (an examination or test).
- To cover and warm eggs for hatching, as a fowl; to brood; to incubate.
- To take a position for the purpose of having some artistic representation of oneself made, such as a picture or a bust.
- To have position, as at the point blown from; to hold a relative position; to have direction.
- Short for situation.