Pick up child likely to make mischief and wander (7)
I believe the answer is:
improve
'pick up' is the definition.
(I've seen this before)
'mischief and wander' is the wordplay.
'mischief' becomes 'imp' (mischievous creature).
'and' says to put letters next to each other.
'wander' becomes 'rove' (synonyms).
'imp'+'rove'='IMPROVE'
'child likely to make' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for improve that I've seen before include "Get or make better" , "Make progress" , "Become better" , "reform" , "Polish" .)