Cool, practical jars contain rum (10)
I believe the answer is:
unromantic
'cool practical' is the definition.
(unromantic can mean unsentimental and practical)
'jars contain rum' is the wordplay.
'jars' indicates anagramming the letters (the letters must be shocked or jarred).
'contain'+'rum'='containrum'
'containrum' is an anagram of 'UNROMANTIC'.
(Other definitions for unromantic that I've seen before include "without affection?" , "displaying no outward affection" , "As classical music may be narrowly called" , "Hard-headed" , "Not loving or amorous" .)