Prosper when the Bureau accepts defeat (7)
I believe the answer is:
blossom
'prosper' is the definition.
The definition and answer can be both related to change as well as being verbs in their base form.
Perhaps there's an association between them I don't understand?
'the bureau accepts defeat' is the wordplay.
I cannot quite see how this works, but
'defeat' could be 'loss' (I've seen this in other clues) and 'loss' is located in the answer.
This explanation may well be incorrect...
'when' acts as a link.
Can you help me to learn more?
(Other definitions for blossom that I've seen before include "Bloom" , "Produce flowers" , "Flowers on, eg, cherry" , "Yield flowers" , "Girl - flower(s)" .)