Goddess -- one without love, one in muddle (7)
I believe the answer is:
nemesis
'goddess' is the definition.
(I've seen this before)
'one without love one in muddle' is the wordplay.
'without' is a deletion indicator.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'one' becomes 'i' (Roman numeral).
'in' means one lot of letters goes inside another.
'muddle' becomes 'mess' ('mess' can be a synonym of 'muddle'**).
'one' with 'o' taken out is 'ne'.
'i' going within 'mess' is 'mesis'.
'ne'+'mesis'='NEMESIS'
(Other definitions for nemesis that I've seen before include "Agent of (someone's) downfall" , "Fate" , "enemy" , "causes downfall" , "Something causing misery (or death) - Meissen (anag)" .)