What has no members — originally thirty, approximately (5)
I believe the answer is:
torso
'what has no members' is the definition.
I can't tell whether this defines the answer.
'originally thirty approximately' is the wordplay.
'originally' indicates taking the first letters.
'approximately' becomes 'or so' (synonyms).
The initial letter of 'thirty' is 't'.
't'+'orso'='TORSO'
Can you help me to learn more?
(Other definitions for torso that I've seen before include "Chest" , "upper body" , "Limbless statue" , "Roost on trunk?" , "Trunk, something unfinished" .)