The most common and most likely answer to this crossword clue is the 8 letter word WINGLESS
I've seen this crossword clue in The Times
W
I
N
G
L
E
S
S
More clues leading to the result WINGLESS
Buddy explains!
The straight part
We know that "Like rugby side that’s lost player/unable to leave the ground" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case like rugby side that’s lost player/unable to leave the ground = wingless.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.