Though faint-hearted, moves smartly (6)
I believe the answer is:
tweaks
'though faint-hearted moves smartly' is the definition.
I can't judge whether this definition defines the answer.
'faint-hearted moves smartly' is the wordplay.
'faint' becomes 'weak' (similar in meaning).
'hearted' means one lot of letters goes inside another (some letters go to the heart of the word).
'moves smartly' becomes 'ts' (I can't explain this - if you can you should give a lot more credence to this answer).
'weak' placed inside 'ts' is 'TWEAKS'.
Can you help me to learn more?
(Other definitions for tweaks that I've seen before include "Improves a little" , "Pinches and twists, perhaps nose" , "Makes little adjustments" , "Pinches and twists, maybe a nose" , "Some fine tuning" .)