Force rascal to join the Spanish (5)
I believe the answer is:
impel
'force' is the definition.
(I know that force can be written as impel)
'rascal to join the spanish' is the wordplay.
'rascal' becomes 'imp' (synonyms).
'to join' means one lot of letters go next to another.
'the spanish' becomes 'el' ('the' in Spanish).
'imp'+'el'='IMPEL'
(Other definitions for impel that I've seen before include "'Drive, force (5)'" , "Force to act" , "Press on - drive forward" , "Cause to move forward" , "Urge or propel" .)