Rosemary, perhaps enthralled by Christopher Biggins (4)
I believe the answer is:
herb
'rosemary perhaps' is the definition.
(rosemary is a kind of herb)
'enthralled by christopher biggins' is the wordplay.
'enthralled by' indicates a hidden word.
'HERB' is hidden in the letters of 'christopher biggins'.
(Other definitions for herb that I've seen before include "Useful or edible plant" , "Bouquet garni component" , "Plant used for flavour" , "Wayside plant with small red flowers" , "Parsley, for instance" .)