The most common and most likely answer to this crossword clue is the 7 letter word WICKETS
I've seen this crossword clue in Independent
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More clues leading to the result WICKETS
Buddy explains!

The straight part
We know that "which fielding sides want" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case which fielding sides want = wickets.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 WICKETS mean?
WICKETS noun- A small door or gate, especially one beside a larger one.
- A small window or other opening, sometimes fitted with a grating.
- A service window, as in a bank or train station, where a customer conducts transactions with a teller; a ticket barrier at a rail station, box office at a cinema, etc.
- One of the two wooden structures at each end of the pitch, consisting of three vertical stumps and two bails; the target for the bowler, defended by the batsman.
- A dismissal; the act of a batsman getting out.
- The period during which two batsmen bat together.
- The pitch.
- The area around the stumps where the batsmen stand.
- Any of the small arches through which the balls are driven.
- A temporary metal attachment that one attaches one's lift-ticket to.
- A shelter made from tree boughs, used by lumbermen.
- The space between the pillars, in post-and-stall working.
- An angle bracket when used in HTML.