Soft material, effective protecting old whisky (9)
I believe the answer is:
towelling
'soft material' is the definition.
(cloth material)
'effective protecting old whisky' is the wordplay.
'effective' becomes 'telling' (synonyms).
'protecting' is an insertion indicator (inserted letters are held or protected).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'whisky' becomes 'W' (phonetic alphabet: alpha, bravo, charlie etc.).
'o'+'w'='ow'
'telling' going around 'ow' is 'TOWELLING'.
(Other definitions for towelling that I've seen before include "Bathrobe fabric" , "Terry" , "Absorbent cloth" .)