The most common and most likely answer to this crossword clue is the 7 plus 4 letter word PHANTOM LIMB
I've seen this crossword clue in The Guardian
P
H
A
N
T
O
M
L
I
M
B
Buddy explains!
The straight part
We know that "a member there in spirit? /a member there in spirit?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a member there in spirit? /a member there in spirit? = phantom limb.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.