I'm taking a long time to get the picture (5)
I believe the answer is:
image
'the picture' is the definition.
(synonyms)
'i'm taking a long time' is the wordplay.
'taking' says to put letters next to each other.
'a long time' becomes 'age' (an age is a period of time).
'im'+'age'='IMAGE'
'to get' acts as a link.
(Other definitions for image that I've seen before include "Visual or mental representation" , "Metaphor; figure" , "Likeness, could be spitting" , "Effigy, icon" , "Dead ringer" .)