Ring back around lunchtime to get Plant (5)
I believe the answer is:
lilac
'plant' is the definition.
(type of plant)
'ring back around lunchtime' is the wordplay.
'ring' becomes 'call' (call on the phone).
'back' shows that the letters should be reversed in order.
'around' is an insertion indicator.
'lunchtime' becomes 'I' (one o'clock is I on a clock with Roman numerals).
'call' backwards is 'llac'.
'llac' enclosing 'i' is 'LILAC'.
'to get' acts as a link.
(Other definitions for lilac that I've seen before include "Fragrant shrub; colour" , "Pinkish purple - shrub" , "Shrub with fragrant pink, purple or white flowers" , "Purplish in colour" , "Pale pinkish-violet" .)