It's stupid to give a fathead credit (5)
I believe the answer is:
crass
'it's stupid' is the definition.
(I've seen this in another clue)
'a fathead credit' is the wordplay.
I cannot quite understand how this works, but
'a' is found in the answer.
'credit' could be 'cr' and 'cr' is found within the answer.
This may be the basis of clue (or it may be nonsense).
'to give' is the link.
Can you help me to learn more?
(Other definitions for crass that I've seen before include "Witless" , "'Gross, vulgar (5)'" , "Blundering" , "Coarse" , "Indelicate" .)