Though solid in form, they may have fragile footing (5)
I believe the answer is:
idols
'may have fragile footing' is the definition.
I can't tell whether this definition defines the answer.
'though solid in form they' is the wordplay.
'solid' can be anagrammed to 'IDOLS'.
But, I am unsure how the anagram is indicated.
Can you help me to learn more?
(Other definitions for idols that I've seen before include "Graven images sometimes worshipped" , "Effigies worshipped as gods" , "objects such as the Golden Calf" , "Objects of worship" , "False gods" .)