A learner seen with sweetheart everywhere (3,4)
I believe the answer is:
all over
'everywhere' is the definition.
(I've seen this before)
'a learner seen with sweetheart' is the wordplay.
'learner' becomes 'l'.
'seen with' says to put letters next to each other.
'sweetheart' becomes 'lover' (I've seen this before).
'a'+'l'+'lover'='ALL-OVER'
(Other definitions for all over that I've seen before include "very characteristically" , "typically" , "Everywhere (bar the shouting?)" , "Obsessed with" , "Excessively attentive" .)