Fasten loosely with a little nail (4)
I believe the answer is:
tack
This could be a double definition.
'fasten loosely' is the first definition.
'tack' can be an answer for 'fasten' (tacking is a kind of fastening). I am unsure of the 'loosely' bit.
'little nail' is the second definition.
'tack' can be an answer for 'nail' (I've seen this before). I'm not sure about the 'little' bit.
'with a' is the link.
Can you help me to learn more?
(Other definitions for tack that I've seen before include "Cheap material; nail" , "Type of nail" , "Short, flat-headed nail" , "Stable gear" , "Stickiness" .)