Joke about face of ruthless islander, heartless as a giant (10)
I believe the answer is:
gargantuan
'giant' is the definition.
(synonyms)
'joke about face of ruthless islander heartless as a' is the wordplay.
I cannot quite understand how this works, but
'about' could be 'a' (abbreviation in Chambers) and 'a' is located in the answer.
'a' could be 'an' and 'an' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for gargantuan that I've seen before include "Prodigious" , "Stupendously big" , "Elephantine" , "Huge" , "Enormous" .)