A lion ate Rob, the tumbler (7)
I believe the answer is:
acrobat
'tumbler' is the definition.
(synonyms)
'a lion ate rob' is the wordplay.
'lion' becomes 'cat' (lions are big cats).
'ate' is an insertion indicator.
'cat' going around 'rob' is 'crobat'.
'a'+'crobat'='ACROBAT'
'the' is the link.
(Other definitions for acrobat that I've seen before include "Spectacular gymnast" , "Gymnastic entertainer" , "performer of risky feats?" , "Taco bar (anag.)" , "circus artiste" .)