Ramble inside improvement (4)
I believe the answer is:
rove
'ramble' is the definition.
(I know that ramble can be written as rove)
'inside improvement' is the wordplay.
'inside' indicates the answer is hidden within the clue.
'ROVE' is hidden within 'improvement'.
(Other definitions for rove that I've seen before include "Range" , "Wander aimlessly" , "Wander or walk about" , "Roam about aimlessly" , "Knock about" .)