The expandable part can be termed "giant" (5)
I believe the answer is:
panda
'be termed giant' is the definition.
I can't tell whether this definition defines the answer.
'the expandable part' is the wordplay.
'part' says the answer is hidden in the clue.
'PANDA' can be found hidden inside 'expandable'.
'can' is the link.
Can you help me to learn more?
(Other definitions for panda that I've seen before include "Black and white beast" , "Large bear from the bamboo forests of China and Tibet" , "One bearlike" , "Endangered bamboo eater" , "Racoon-like animal" .)