Bob, for instance, or I had to be replaced (6)
I believe the answer is:
hairdo
'bob for instance' is the definition.
(bob is a type of hairdo)
'or i had to be replaced' is the wordplay.
'to be replaced' indicates an anagram.
'or'+'i'+'had'='orihad'
'orihad' with letters rearranged gives 'HAIRDO'.
(Other definitions for hairdo that I've seen before include "The process of styling hirsute head" , "capital arrangement" , "Possibly cut" , "Eg, beehive or mullet" , "Styling of the locks" .)