A solid shape once adjusted (4)
I believe the answer is:
cone
'a solid shape' is the definition.
'cone' can be an answer for 'shape' (cone is a kind of shape). I'm unsure of the 'a solid' bit.
'once adjusted' is the wordplay.
'adjusted' is an anagram indicator.
'once' anagrammed gives 'CONE'.
Can you help me to learn more?
(Other definitions for cone that I've seen before include "Volcanic peak" , "may obstruct lane" , "Tapering object" , "Figure (for traffic control?)" , "children can lick" .)