There's a trace of uranium in many a flower (5)
I believe the answer is:
lotus
'a flower' is the definition.
(I know that Lotus is a type of flower)
'there's a trace of uranium in many' is the wordplay.
'there's a trace of' says to take the initial letters.
'in' is an insertion indicator.
'many' becomes 'lots' (lots of something).
The first letter of 'uranium' is 'u'.
'u' put within 'lots' is 'LOTUS'.
(Other definitions for lotus that I've seen before include "Kind of cross-legged position for meditation" , "Sacred Egyptian water lily" , "Car manufacturer - plant" , "reason for indolence" , "In myth, a plant whose fruit induced forgetfulness" .)