Spell of cold weather eventually penetrating the joint (5)
I believe the answer is:
charm
'spell' is the definition.
(a charm is a magic spell)
'cold weather eventually penetrating the joint' is the wordplay.
'cold' becomes 'c' (eg on taps).
'eventually' suggests the final letters.
'penetrating' indicates putting letters inside.
'the joint' becomes 'ham' (ham is a joint of meat).
The last letter of 'weather' is 'r'.
'r' put inside 'ham' is 'harm'.
'c'+'harm'='CHARM'
'of' is the link.
(Other definitions for charm that I've seen before include "Make delighted" , "Greatly delight" , "Entice" , "small ornament" , "Trinket on a bracelet" .)