Put it in guard's tower (4)
I believe the answer is:
stow
'put' is the definition.
(stowing is a kind of putting)
'in guard's tower' is the wordplay.
'in' indicates a hidden word.
'STOW' can be found hidden inside 'guards tower'.
'it' is the link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for stow that I've seen before include "Pack, put away" , "Store away tidily" , "- - -on-the-Wold" , "Fill by packing tightly" , "Keep under hatches" .)