Average dad's skilful gripping head of screwdriver (8)
I believe the answer is:
passable
'average' is the definition.
(thesaurus)
'dad's skilful gripping head of screwdriver' is the wordplay.
'dad's' becomes 'pas' ('pa' can be a synonym of 'dad').
'skilful' becomes 'able' (I've seen this before).
'gripping' means one lot of letters goes inside another.
'head of' says to take the initial letters.
The first letter of 'screwdriver' is 's'.
'pas'+'able'='pasable'
'pasable' enclosing 's' is 'PASSABLE'.
(Other definitions for passable that I've seen before include "not hogging the road" , "OK" , "examinations should be!" , "Barely adequate" , "All right" .)