Guy, 50, a prickly type (6)
I believe the answer is:
teasel
'a prickly type' is the definition.
(prickly plant)
'guy 50' is the wordplay.
'guy' becomes 'tease' (I've seen this before).
'50' becomes 'l' ('L' can be a synonym of '50').
'tease'+'l'='TEASEL'
(Other definitions for teasel that I've seen before include "Sat Lee down on the spiny herb" , "Spiny flower head" , "Prickly plant (S, not Z)" , "it helps us to nap" , "Plant with prickly flower head" .)