Bloomer made by union leader in stiffly formal city (7)
I believe the answer is:
primula
'bloomer' is the definition.
(I've seen this before)
'union leader in stiffly formal city' is the wordplay.
'leader' says to take the initial letters.
'in' is an insertion indicator.
'stiffly formal' becomes 'prim' (I've seen this before).
'city' becomes 'la' (Los Angeles).
The first letter of 'union' is 'u'.
'prim'+'la'='primla'
'u' put inside 'primla' is 'PRIMULA'.
'made by' is the link.
(Other definitions for primula that I've seen before include "Flowering plant" , "Cowslip genus" , "Primrose" , "Spring flower" , "Air plum, oddly, from this plant" .)