Choose pence before pounds - no problem! (6)
I believe the answer is:
please
'choose' is the definition.
(thesaurus)
'pence before pounds no problem' is the wordplay.
'pence' becomes 'p'.
'before' says to put letters next to each other.
'pounds' becomes 'L' (L can represent the monetary pound).
'no problem' becomes 'ease' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'p'+'l'+'ease'='PLEASE'
Can you help me to learn more?
(Other definitions for please that I've seen before include "Polite request - make someone happy" , "Make cheerful" , "Delight; amuse" , "Make glad, being asleep" , "cheer up" .)