Weight of American's male organ (4)
I believe the answer is:
heft
'weight' is the definition.
(I know that heft is a type of heaviness)
'american's male organ' is the wordplay.
I cannot quite see how this works, but
'male' could be 'he' (he refers to a man) and 'he' is located in the answer.
This explanation may well be incorrect...
'of' is the link.
Can you help me to learn more?
(Other definitions for heft that I've seen before include "Feel the weight of" , "Try to determine weight by lifting" , "Lift (something heavy)" , "Lift in order to heave, say an axe" , "Lift or hold something to assess its weight" .)