The Spanish poet returns to keep university strong (7)
I believe the answer is:
durable
'strong' is the definition.
(thesaurus)
'the spanish poet returns to keep university' is the wordplay.
'the spanish' becomes 'el' ('the' in Spanish).
'poet' becomes 'bard' (bard is a kind of poet).
'returns' is a reversal indicator.
'to keep' indicates putting letters inside.
'university' becomes 'U' (abbreviation for university).
'el'+'bard'='elbard'
'elbard' in reverse letter order is 'drable'.
'drable' enclosing 'u' is 'DURABLE'.
(Other definitions for durable that I've seen before include "Capable of lasting" , "Hardy" , "Good" , "Long-lasting and hard-wearing" , "existing for a long time" .)