Small clothes, I do declare! (5)
I believe the answer is:
swear
'do declare' is the definition.
(swearing is a kind of declaring)
'small clothes i' is the wordplay.
I cannot quite understand how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is present in the answer.
'clothes' could be 'wear' (synonyms) and 'wear' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for swear that I've seen before include "Promise on oath" , "Express annoyance" , "Solemnly promise" , "Eff and blind" , "Use indecent or blasphemous language" .)