Fragrant flower
There are a few possibilities for this:
(Other definitions for sweetpea that I've seen before include "climbing plant" , "climber" .)
'fragrant flower' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gardenia that I've seen before include "A reading (anag.)" , "Drainage for shrub with white or yellow flowers" , "Shrub with fragrant flowers - in Grade A (anag)" , "Shrub such as the Cape jasmine" , "bloomer!" .)
(Other definitions for tuberose that I've seen before include "This plant outs beer, strangely" , "To be sure (anag.)" , "Like a potato" , "with knobs" .)