Threaten to take head off flower (4)
I believe the answer is:
loom
'threaten' is the definition.
(something threatening might loom over you)
'head off flower' is the wordplay.
'head off' means to remove the first letter.
'flower' becomes 'bloom' (synonyms).
'bloom' with its first letter removed is 'LOOM'.
'to take' is the link.
(Other definitions for loom that I've seen before include "Impend; weaving machine" , "Textile machine; come into sight" , "Weaving frame - seem ominously close" , "Mill machinery" , "Appear dimly; be imminent" .)