Beer with no head? That is a bit sinister! (5)
I believe the answer is:
eerie
'sinister' is the definition.
(I've seen this before)
'beer with no head? that is' is the wordplay.
'with no head?' means to remove the first letter (I've seen 'with no head' mean this).
'that is' becomes 'ie' (abbreviation for id est, 'that is' in Latin).
'beer' with its first letter taken off is 'eer'.
'eer'+'ie'='EERIE'
'a bit' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for eerie that I've seen before include "Spooky, unearthly" , "Frighteningly odd" , "Strange and disturbing" , "Uncannily strange" , "Spooky, supernatural" .)