Lying porter regularly caught dipping into change (13)
I believe the answer is:
prevarication
'lying' is the definition.
(I know that lying can be written as prevarication)
'porter regularly caught dipping into change' is the wordplay.
'porter regularly' becomes 'pre' (I can't explain this - if you can you should believe this answer much more).
'caught' becomes 'c' (cricket abbreviation).
'dipping into' is an insertion indicator.
'change' becomes 'variation' (variation is a kind of change).
'c' put into 'variation' is 'varication'.
'pre'+'varication'='PREVARICATION'
(Other definitions for prevarication that I've seen before include "Evasive speech or deeds" , "Evasive behaviour" .)