Wobbly old picture (5)
I believe the answer is:
rocky
'wobbly' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for rocky that I've seen before include "'-' Marciano, US boxer" , "Unsteady; like boulders" , "Characterised by large stones" , "Uneven" , "likely to collapse" .)