Suspect everybody returned in term as planned (5,1,3)
I believe the answer is:
smell a rat
'suspect' is the definition.
(I've seen this before)
'everybody returned in term as planned' is the wordplay.
'everybody' becomes 'all' (I've seen this before).
'returned' is a reversal indicator.
'in' is an insertion indicator.
'planned' indicates anagramming the letters.
'all' reversed gives 'lla'.
'term'+'as'='termas'
'termas' anagrammed gives 'smerat'.
'lla' going within 'smerat' is 'SMELL A RAT'.
(Other definitions for smell a rat that I've seen before include "Sense something suspicious" , "Detect something suspicious" , "Suspect something's amiss" , "Suspect trickery (colloq.)" , "Suspect deception" .)