Sister merrily lowering her head to be awkward (8)
I believe the answer is:
ungainly
'awkward' is the definition.
(synonyms)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for ungainly that I've seen before include "Physically clumsy or maladroit" , "Gangling" , "Lacking grace in movement" , "Clumsly, maladroit" , "Clumsy or awkward, as nun gaily goes about" .)