Sudden increase in desire after slow beginning (5)
I believe the answer is:
surge
'sudden increase' is the definition.
(a surge is a sudden increase in something)
'desire after slow beginning' is the wordplay.
'desire' becomes 'urge' (I've seen this in another clue).
'after' means one lot of letters go next to another.
'slow beginning' becomes 's' (I can't justify this - if you can you should believe this answer much more).
'urge' put after 's' is 'SURGE'.
'in' is the link.
Can you help me to learn more?
(Other definitions for surge that I've seen before include "Rolling swell of the sea" , "Move rapidly forward like a wave" , "roll" , "Sudden onward motion" , "Sudden powerful increase" .)