Is about to get up the flags (6)
I believe the answer is:
irises
'the flags' is the definition.
(I've seen this before)
'is about to get up' is the wordplay.
'about' indicates putting letters inside.
'to get up' becomes 'rise' ('rise' can be a synonym of 'get up').
'is' placed around 'rise' is 'IRISES'.
(Other definitions for irises that I've seen before include "Is sire in favour of flowers?" , "Parts of eyes or flowering plants" , "Eye membranes or showy flowers." , "Subject for van Gogh" , "Expensive painting" .)