Don't mention it to Allan, confused about time (3,2,3)
I believe the answer is:
not at all
'don't mention it' is the definition.
(I've seen this before)
'to allan confused about time' is the wordplay.
'confused' indicates an anagram.
'about' means one lot of letters goes inside another.
'time' becomes 't'.
'to'+'allan'='toallan'
'toallan' with letters rearranged gives 'noatall'.
'noatall' placed around 't' is 'NOT AT ALL'.
(Other definitions for not at all that I've seen before include "Never!" , "My pleasure" , "In no way" , "You're welcome" , "Don't mention it!" .)