Trouble experienced reversing small bloomers (7)
I believe the answer is:
dahlias
'bloomers' is the definition.
(I've seen this before)
'trouble experienced reversing small' is the wordplay.
'trouble' becomes 'ail' (synonyms).
'experienced' becomes 'had' (have can mean to experience or go through).
'reversing' says the letters should be written backwards.
'small' becomes 's' (abbreviation - e.g. clothes size).
'ail'+'had'='ailhad'
'ailhad' in reverse letter order is 'dahlia'.
'dahlia'+'s'='DAHLIAS'
(Other definitions for dahlias that I've seen before include "I had Al's fowers" , "Tuberous Mexican flowers" , "Might Ali dash for the flowers?" , "'Hid, alas, among the flowers (7)'" , "Tuberous garden plants" .)