Tough strapping! (6)
I believe the answer is:
strong
I believe this is a double definition.
'tough' is the first definition.
(associated in meaning)
'strapping' is the second definition.
(synonyms)
(Other definitions for strong that I've seen before include "firm" , "is excelling" , "strong" , "Physically powerful - feel 1 Across" , "Powerful; full-flavoured" .)