American uncle — strong man losing son (3)
I believe the answer is:
sam
'american uncle' is the definition.
(Uncle Sam is a nickname for the USA)
'strong man losing son' is the wordplay.
'strong man' becomes 'samson' (I've seen this before).
'losing' suggests deleting specific letters.
'samson' with 'son' taken out is 'SAM'.
(Other definitions for sam that I've seen before include "Boy" , "Uncle" , "together once" , "Casablanca piano player" .)