Set one’s heart on a top part (6)
I believe the answer is:
aspire
'set' is the definition.
The definition and answer can be both related to thinking as well as being verbs in their base form.
Maybe they are linked in a way I don't understand?
'one's heart on a top part' is the wordplay.
'one's' becomes 'a's' (a thing is one thing).
'heart on a top' becomes 'pi' (I can't explain this - if you can you should give a lot more credence to this answer).
'part' becomes 're' (re is a kind of part).
'as'+'pi'+'re'='ASPIRE'
Can you help me to learn more?
(Other definitions for aspire that I've seen before include "Have a strong desire to achieve something" , "Strive for higher things" , "Desire (to reach higher things)" , "Seek (to do something)" , "Have ambitions (to achieve something)" .)