Hard like that hat (5)
I believe the answer is:
solid
'hard' is the definition.
(associated in meaning)
'like that hat' is the wordplay.
'like that' becomes 'so' (as in 'like so').
'hat' becomes 'lid' (lid can informally mean a hat).
'so'+'lid'='SOLID'
(Other definitions for solid that I've seen before include "thick" , "Hard and compact" , "Three-dimensional shape, not hollow" , "Firm; not liquid" , "Firm - sound - reliable" .)