Arrived, having secured posh car to roll up for tea (8)
I believe the answer is:
camomile
'tea' is the definition.
(I've seen this before)
'arrived having secured posh car to roll up' is the wordplay.
'arrived' becomes 'came' (coming is a kind of arriving).
'having secured' is an insertion indicator.
'posh car' becomes 'limo'.
'to roll up' says the letters should be written in reverse (I've seen 'rolling up' mean this).
'limo' reversed gives 'omil'.
'came' placed around 'omil' is 'CAMOMILE'.
'for' acts as a link.
(Other definitions for camomile that I've seen before include "Plant for tea or lawn" , "Ma, Clio and me have medicinal tea" , "Plant used for making herbal drink" , "Fragrant plant" , "Wild flower used medicinally and for tea" .)