Strongly and solidly built (6)
I believe the answer is:
sturdy
'strongly and solidly built' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for sturdy that I've seen before include "Well-constructed" , "Stout, brawny" , "Strong and solidly built" , "Strong and sturdily built" , "Solidly made" .)