Pleased Lou is working in the plant (9)
I believe the answer is:
gladiolus
'the plant' is the definition.
The answer is an example.
'pleased lou is working' is the wordplay.
'pleased' becomes 'glad' (similar in meaning).
'working' is an anagram indicator.
'lou'+'is'='louis'
'louis' anagrammed gives 'iolus'.
'glad'+'iolus'='GLADIOLUS'
'in' acts as a link.
(Other definitions for gladiolus that I've seen before include "Plant of iris family" , "Flower" .)