He has the heart of a giant (3)
I believe the answer is:
ian
'he' is the definition.
'the heart of a giant' is the wordplay.
'the heart of' indicates a hidden word.
'IAN' is hidden within 'giant'.
'has' is the link.
(Other definitions for ian that I've seen before include "Boy's name (Scottish?)" , "... Fleming, author of the Bond books" , "Botham or Chappell?" , "The familiar Dr Paisley" , "Sir - McKellen, actor" .)