A couple of lines crossing everywhere (3,4)
I believe the answer is:
all over
'everywhere' is the definition.
(I've seen this before)
'a couple of lines crossing' is the wordplay.
'a couple of lines' becomes 'all' (I've seen this in other clues).
'crossing' becomes 'over' (I can't justify this - if you can you should give a lot more credence to this answer).
'all'+'over'='ALL-OVER'
Can you help me to learn more?
(Other definitions for all over that I've seen before include "Excessively attentive" , "Everywhere (bar the shouting?)" , "Obsessed with" , "covering everything" , "very characteristically" .)