Extremely tiny royal woman with head of year making cruel rule (7)
I believe the answer is:
tyranny
'cruel rule' is the definition.
(I've seen this in another clue)
'extremely tiny royal woman with head of year' is the wordplay.
'extremely' says to hollow out the word (remove centre letters) (only the extremes of the word are used).
'royal' becomes 'r' (abbreviation).
'woman' becomes 'ann' (woman's name).
'with head of' indicates taking the first letters.
'tiny' with its middle removed is 'ty'.
The initial letter of 'year' is 'y'.
'ty'+'r'+'ann'+'y'='TYRANNY'
'making' acts as a link.
(Other definitions for tyranny that I've seen before include "Excessive use of power" , "Dominance through threat of punishment and violence" , "Form of despotism" , "Dictatorship" , "Cruel and oppressive rule" .)