Most of catalogue a little reduced, showing flexibility (6)
I believe the answer is:
lissom
'showing flexibility' is the definition.
(lissome or lissom means supple)
'most of catalogue a little reduced' is the wordplay.
'most of' means to remove the last letter.
'catalogue' becomes 'list' (a catalogue is a list of items).
'a little' becomes 'some' (both can mean a small amount).
'reduced' means to remove the last letter.
'list' with its last letter removed is 'lis'.
'some' with its last letter taken away is 'som'.
'lis'+'som'='LISSOM'
(Other definitions for lissom that I've seen before include "Supple or agile" , "Lithe, nimble" , "Supple, nimble" , "Gracefully slim and supple" , "Lithe and flexible" .)