Use dinosaur egg initially the wrong way (5)
I believe the answer is:
exert
'use' is the definition.
(exerting is a kind of using)
'dinosaur egg initially the wrong way' is the wordplay.
'dinosaur' becomes 'T Rex' (abbreviation for Tyrannosaurus Rex).
'initially' indicates taking the first letters.
'the wrong way' is a reversal indicator.
The first letter of 'egg' is 'e'.
'trex'+'e'='trexe'
'trexe' reversed gives 'EXERT'.
(Other definitions for exert that I've seen before include "Employ" , "Work strenuously" , "Bring into use, strength or influence" , "Cartoon 4 across" , "Wield - apply" .)