Flower I telephone back about (5)
I believe the answer is:
lilac
'flower' is the definition.
(I've seen this before)
'i telephone back about' is the wordplay.
'telephone' becomes 'call' (synonyms).
'back' says the letters should be written in reverse.
'about' indicates putting letters inside.
'call' written backwards gives 'llac'.
'i' put inside 'llac' is 'LILAC'.
(Other definitions for lilac that I've seen before include "Shrub or small tree with fragrant blossom" , "Mauve-like colour" , "Flowering tree of the olive family" , "Pinkish purple - shrub" , "Shade" .)