Pleasing key to solving clue on time (6)
I believe the answer is:
dulcet
'pleasing' is the definition.
(thesaurus)
'key to solving clue on time' is the wordplay.
'key' becomes 'd' (musical key).
'to solving' is an anagram indicator (anagrams are puzzles).
'on' indicates putting letters inside (as in clothing 'on' a person).
'time' becomes 't' (abbreviation).
'clue' is an anagram of 'ulce'.
'd' going within 'ulce' is 'dulce'.
'dulce'+'t'='DULCET'
(Other definitions for dulcet that I've seen before include "DT clue (anag.)" , "Of voice or tone, sweet-sounding" , "Mellifluous, pleasant to the ear" , "Soft and pleasant sounding" , "Sweet-sounding, melodious" .)