Figure is round and not totally lifeless (6)
I believe the answer is:
isogon
'figure' is the definition.
(I have seen 'Regular figure' mean 'isogon' so perhaps 'figure' could also mean 'isogon')
'is round and not totally lifeless' is the wordplay.
'round' says the letters should be written in reverse.
'and' becomes 'n' (common abbreviation for 'and').
'not' becomes 'o' (I've seen this in other clues).
'totally lifeless' becomes 'go' (I can't explain this - if you can you should give a lot more credence to this answer).
'n'+'o'+'go'='nogo'
'nogo' written backwards gives 'ogon'.
'is'+'ogon'='ISOGON'
Can you help me to learn more?
(Other definitions for isogon that I've seen before include "Equilateral triangle, say" , "Regular figure" , "Equiangular polygon" , "See plane figure" .)