Old men's heads in touch with excess (3,4)
I believe the answer is:
too much
'excess' is the definition.
(I've seen this before)
'old men's heads in touch' is the wordplay.
'heads' indicates taking the first letters.
'in' indicates putting letters inside.
The initial letters of 'old mens' is 'om'.
'om' going into 'touch' is 'TOO MUCH'.
'with' acts as a link.
(Other definitions for too much that I've seen before include "Excess, more than is needed" , "Excessive, overwhelming" , "More than is reasonable" , "More than is tolerable" , "Beyond endurance" .)