Part of it 'it an iceberg (7)
I believe the answer is:
titanic
'part' is the definition.
Both the answer and definition are adjectives. Perhaps there's an association between them I don't understand?
'of it 'it an iceberg' is the wordplay.
'of' indicates a hidden word.
'TITANIC' can be found hidden inside 'it it an iceberg'.
Can you help me to learn more?
(Other definitions for titanic that I've seen before include "Ship sunk by iceberg" , "Twenty one [SHIP]" , "Huge, like doomed liner that struck iceberg" , "Act in it (anag.)" , "Doomed liner found in attic" .)