Think hard about bit of money put in box (11)
I believe the answer is:
concentrate
'think' is the definition.
(I know that think is a more specific form of the action concentrate)
'hard about bit of money put in box' is the wordplay.
'hard about' becomes 'on' (as in a book 'on' a certain topic. I am not sure about the 'hard' bit.).
'bit of money' becomes 'cent'.
'put in' means one lot of letters goes inside another.
'box' becomes 'crate' (crate is a kind of box).
'on'+'cent'='oncent'
'oncent' inserted inside 'crate' is 'CONCENTRATE'.
Can you help me to learn more?
(Other definitions for concentrate that I've seen before include "get solution in chemistry" , "What thinker may have to do" , "Think" , "Don't daydream!" , "Increase the strength of (a solution)" .)