Ransomware

 When read in clue order, the last letters of extraneous words in every clue provide a partial definition and visual context of a three word phrase indicating the change required to a number of clue answers before entry in the grid.  Solvers must complete and highlight the cryptic representation of that phrase in the completed grid (two words).  All final entries are real words, phrases or proper nouns.

The last letters of each extra word in clue order, provide “TO ALTER THE RULES OF THE GAME AFTER IT HAS BEGUN” and “RUGBY”.  This defines in part “MOVE THE GOALPOSTS” which in a rugby context are H-shaped.  Nine solutions had their H’s moved to provide alternative words.  The two word anagram of THE GOALPOSTS, HOSTAGE PLOTS was to be completed and highlighted.