In close up, a poor start is a bit of a bloomer (5)
I believe the answer is:
sepal
'a bit of a bloomer' is the definition.
(I've seen this before)
'in close up a poor start' is the wordplay.
'in' is an insertion indicator.
'close up' becomes 'seal' (I've seen this before).
'start' indicates taking the first letters.
The first letter of 'poor' is 'p'.
'seal' going around 'p' is 'SEPAL'.
'is' acts as a link.
(Other definitions for sepal that I've seen before include "bit of a bloomer" , "Enclosing part of flower" , "Calyx segment" , "Lapse about part of a flower" , "Part of the calyx of a flower" .)