Get on with 100 + 1 + 100 + 1,000 ÷ 50? (5)
I believe the answer is:
'get on' is the definition.
(if two people click they get on well)
'with 100 1 100 1000 50?' is the wordplay.
'with' says to put letters next to each other.
'l00' becomes 'c' (Roman numeral).
'l l00 l000 50?' becomes 'lick' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'c'+'lick' is 'CLICK'.
(Other definitions for click that I've seen before include "get on" , "a metallic sound" , "Find mutual understanding - operate mouse" , "Become friendly with < > sort of beetle?" , "One can with mouse, too" .)