Popular string instrument at sea oddly dropped -- undamaged (9)
I believe the answer is:
inviolate
'undamaged' is the definition.
(I've seen this before)
'popular string instrument at sea oddly dropped' is the wordplay.
'popular' becomes 'in' ('in' can mean trendy).
'string instrument' becomes 'viol' (historical musical instrument).
'oddly dropped' indicates alternate letters (letters in odd-numbered positions are removed).
The alternating letters of 'sea' are 'e'.
'in'+'viol'+'at'+'e'='INVIOLATE'
(Other definitions for inviolate that I've seen before include "Free from injury" , "unspoiled" , "Entire" , "very safe" , "kept free from damage" .)