Ultimately confusing toilets without identifying symbols (5)
I believe the answer is:
logos
'identifying symbols' is the definition.
(I've seen this in another clue)
'ultimately confusing toilets without' is the wordplay.
'ultimately' suggests the final letters.
'toilets' becomes 'loos' (loo means a toilet).
'without' means one lot of letters goes inside another.
The last letter of 'confusing' is 'g'.
'g' going within 'loos' is 'LOGOS'.
(Other definitions for logos that I've seen before include "philosophical principle" , "The Word of God" .)