Key article delayed increase (8)
I believe the answer is:
escalate
'increase' is the definition.
(I know that escalate is a more specific form of increase)
'key article delayed' is the wordplay.
'key' becomes 'esc' ('Escape' key on a computer keyboard).
'article' becomes 'a' (the indefinite article in English).
'delayed' becomes 'late' (running late).
'esc'+'a'+'late'='ESCALATE'
(Other definitions for escalate that I've seen before include "mushroom" , "Tease Cal badly and mount up" , "Quickly increase in scale" , "mount in tension" , "Magnify" .)