Bulgarian capital trained tree to be young in form (7)
I believe the answer is:
leveret
'young in form' is the definition.
The definition and answer can be both animals as well as being singular nouns.
Maybe there's a link between them I don't understand?
'bulgarian capital trained tree' is the wordplay.
'bulgarian capital' becomes 'lev' (I can't explain this - if you can you should give a lot more credence to this answer).
'trained' is an anagram indicator (to train can mean to grow something into a shape).
'tree' is an anagram of 'eret'.
'lev'+'eret'='LEVERET'
'to be' is the link.
Can you help me to learn more?
(Other definitions for leveret that I've seen before include "Little beast" , "Young bounder" , "Young hare" , "Fast runner, potentially" , "hare about in spring" .)