Lizard -- try grabbing neck but not head (5)
I believe the answer is:
gecko
'lizard' is the definition.
(I know that gecko is a type of lizard)
'try grabbing neck but not head' is the wordplay.
'try' becomes 'go' (both can mean an attempt).
'grabbing' indicates putting letters inside.
'but not head' means to remove the first letter.
'neck' with its first letter taken away is 'eck'.
'go' placed around 'eck' is 'GECKO'.
(Other definitions for gecko that I've seen before include "Cold-blooded type" , "Cold-blooded creature" , "one climbing the walls?" , "Nocturnal lizard" , "Small lizard with adhesive foot-pads" .)