Some Chelsea geriatric is as keen as mustard (5)
I believe the answer is:
eager
'keen as mustard' is the definition.
I can't judge whether this definition defines the answer.
'some chelsea geriatric is' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'EAGER' is hidden within 'chelsea geriatric is'.
'as' acts as a link.
Can you help me to learn more?
(Other definitions for eager that I've seen before include "Like some beavers" , "Keen, avid" , "Keen - enthusiastic" , "Low platform" , "Anxious" .)