Artist to overhaul image — time to grasp medium (9)
I believe the answer is:
rembrandt
'artist' is the definition.
(Rembrandt is an example)
'overhaul image time to grasp medium' is the wordplay.
'overhaul image' becomes 'rebrand'.
'time' becomes 't'.
'to grasp' is an insertion indicator.
'medium' becomes 'm' (as in UK clothing sizes).
'rebrand'+'t'='rebrandt'
'rebrandt' placed around 'm' is 'REMBRANDT'.
'to' acts as a link.
(Other definitions for rembrandt that I've seen before include "One notably exhibited" , "Dutch painter, d. 1669" , "Dutch painter, 1606-69" , "old master" , "Dutch seventeenth-century artist" .)