Summon - percussion has increased (4,2)
I believe the answer is:
drum up
'summon' is the definition.
The answer and definition can be both to do with contact as well as being verbs in their base form.
Perhaps they are linked in a way I don't understand?
'percussion has increased' is the wordplay.
'percussion has' becomes 'drum' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'increased' becomes 'up' (something that's up has increased or risen).
'drum'+'up'='DRUM UP'
Can you help me to learn more?
(Other definitions for drum up that I've seen before include "Attempt to obtain (support)" , "Obtain through vigorous effort - and percussion?" , "Bring about (something) by constant and persistent effort" , "To attract" , "Attempt to get support by canvassing" .)