Reluctant, being attached to the small creature (5)
I believe the answer is:
sloth
'creature' is the definition.
(sloth is a kind of creature)
'reluctant being attached to the small' is the wordplay.
'reluctant' becomes 'loth' ('loth' can be a synonym of 'reluctant').
'being attached to' means one lot of letters go next to another.
'the small' becomes 's' (abbreviation - e.g. clothes size).
'loth' put after 's' is 'SLOTH'.
(Other definitions for sloth that I've seen before include "A deadly sin, being lazy" , "one of a deadly group" , "Indolence" , "Lethargy" , "Laziness; slow mammal" .)