Endless number admire bandit at sea (6)
I believe the answer is:
pirate
'bandit at sea' is the definition.
'endless number admire' is the wordplay.
'endless number' becomes 'pi'.
'admire' becomes 'rate' (I've seen this before).
'pi'+'rate'='PIRATE'
(Other definitions for pirate that I've seen before include "Buccaneer, sea robber" , "Teach, perhaps" , "Sea-robber" , "operating illegally" , "plagiarist" .)