A number make money and gain experience (5)
I believe the answer is:
learn
'gain experience' is the definition.
The definition and answer can be both related to thinking as well as being verbs in their base form.
Perhaps they are linked in a way I don't understand?
'a number make money' is the wordplay.
'a number' becomes 'l' (fifty in Roman numerals).
'make money' becomes 'earn' (I've seen this in another clue).
'l'+'earn'='LEARN'
'and' is the link.
Can you help me to learn more?
(Other definitions for learn that I've seen before include "Succeed in school" , "Renal (anag)" , "Study (at school?)" , "Come to know" , "Be educated" .)