Shrewd copper taking tips from trainee (4)
I believe the answer is:
cute
'shrewd' is the definition.
(I've seen this before)
'copper taking tips from trainee' is the wordplay.
'copper' becomes 'cu' (chemical symbol).
'taking' means one lot of letters go next to another.
'tips from' suggests removing the centre.
'trainee' with its centre taken out is 'te'.
'cu'+'te'='CUTE'
(Other definitions for cute that I've seen before include "Clever - attractive" , "Winsome" , "Charming, quaint" , "Quaintly attractive" , "Attractive and quaint (4" .)